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LECTURE-NOTES 

ON 

CHEMISTRY 

FOR 

DENTAL    STUDENTS 


INCLUDING 

DENTAL    CHEMISTRY   OF    ALLOYS,    AMALGAMS,    ETC. 
SUCH     PORTIONS     OF     ORGANIC      AND      PHYSIOLOGICAL      CHEMISTRY     AS 

HAVE    PRACTICAL    BEARING    ON    THE    SUBJECT    OF    DENTISTRY 

AN     INORGANIC     QUALITATIVE      ANALYSIS     WITH     SPECIALLY     ADAPTED 

BLOWPIPE    AND    MICROSCOPICAL    TESTS,    AND    THE    CHEMICAL 

EXAMINATION    OF    URINE    AND    SALIVA 

BY 

H.   CARLTON  SMITH,  Ph.G. 

LECTURER   ON  PHYSIOLOGICAL   AND   DENTAL   CHEMISTRY   AT    HARVARD    UNIVERSITY 

DENTAL    school;     HONORARY   MEMBER    OF   AMERICAN   ACADEMY    OF   DENTAL 

SCIENCE,    igo6;    OF   THE   METROPOLITAN    SOCIETY    OF   MASSACHUSETTS 

STATE    DENTAL   ASSOCIATION,    I907;    OF   HARVARD    DENTAL 

ALUMNI,    I910;    AND    NORTHERN   OHIO    DENTAL 

ASSOCIATION,    191 2 

SECOND  EDITION  REVISED  AND  ENLARGED 
FIRST    THOUSAND 


NEW   YORK 

JOHN  WILEY  &  SONS 

London:  CHAPMAN  &  HALL,  Limited 

1912 


C  ^qffv^-vOkl.^  ^c^c'^  wvJ2*<  ^'^' 


1^  K  a'lo 


Copyright,  1906,  1912, 

BY 

H.  CARLTON  SMITH 


Stanbope  fliress 

F.    H.  GILSON   COMPANY 
BOSTON,  U.S.A. 


PREFACE   TO   FIRST   EDITION. 


The  arrangement  of  this  book  follows  rather  closely  the 
lecture  course  in  Dental  Chemistry  as  given  by  the  author  at 
the  Harvard  Dental  School.  It  has  been  the  aim  of  these 
lectures  to  give  the  student,  as  concisely  as  possible,  such  por- 
tions of  the  various  branches  of  chemistry  as  are  most  likely 
to  be  of  value  in  practical  work. 

Simplicity  of  manipulation  has  in  some  cases  been  con- 
sidered of  greater  practical  value  than  extreme  accuracy,  es- 
pecially in  the  chapter  on  Quantitative  Analysis,  the  volumetric 
processes  being  given,  as  a  rule,  rather  than  the  more  exact  but 
more  difl&cult  gravimetric  methods. 

The  usual  equipment  of  a  dental  laboratory  has  been  borne 
in  mind,  and  considerable  prominence  given  to  the  simpler 
analytical  tests  made  in  the  dry  way  by  means  of  few  reagents. 

Recent  text-books  and  current  literature  have  been  very 
generally  consulted.  New  tests  have  been  verified  so  far  as 
possible  —  often  modified  —  before  being  recommended  to  the 
student. 

The  U.  S.  Dispensatory  and  the  Newer  Materia  Medica,  as 
given  in  the  Druggists'  Circular,  have  been  drawn  upon  in  the 
sections  on  Local  Anaesthetics  and  Hall 's  and  Essig's  Chemistries 
in  the  section  on  Alloys  and  Amalgams. 

A  chapter  on  Organic  Chemistry  has  been  introduced,  de- 
signed to  furnish  an  understanding  of  this  branch  of  chemical 
science,  which  will  enable  the  student  to  better  comprehend 
the  physiological  chemistry  which  follows. 

The  chapter  on  the  Analysis  of  Saliva  is  one  which  is,  of 


IV  PREFACE   TO   FIRST  AND  SECOND  EDITIONS 

necessity,  incomplete  and  imperfect.  The  investigations  being 
at  present  carried  on  along  the  lines  suggested  by  Dr.  Joseph 
Michaels  of  Paris  and  Dr.  Kirk  of  Philadelphia  are  opening  up 
fields  of  research  of  the  greatest  magnitude  and  of  utmost  im- 
portance, and  they  can  only  be  touched  upon  in  this  work. 

The  atomic  weights  given  are  from  the  international  atomic 
weights  for  1905.     O  =  16. 

In  the  chapter  on  Physiological  Chemistry  the  author  wishes 

to  particularly  acknowledge  his  indebtedness  to  Professor  Wm. 

B.  Hills  of  the  Harvard  Medical  School,  who  furnished  the 

majority  of  the  laboratory  experiments  for  this  portion  of  the 

work. 

H.  C.  S. 

PREFACE   TO   SECOND   EDITION. 


The  second  edition  of  Chemistry  for  Dental  Students  is  an 
almost  new  book,  using  the  first  edition  as  foundation  only. 

The  chapter  on  Organic  Chemistry  has  been  considerably 
enlarged. 

A  number  of  new  cuts,  about  ninety  pages  of  text,  and  eighty- 
five  experiments  have  been  added,  and  the  arrangement  has  been 
changed  with  the  purpose  of  making  the  book  useful  to  any 
teacher  of  Dental  Chemistry.  The  laboratory  work  follows 
closely  the  outline  of  lectures. 

An  effort  has  been  made  to  make  the  chapter  on  Saliva  fairly 
complete  to  date,  June,  191 2,  but  of  course  every  month  brings 
its  added  contribution  of  experiment  and  much  of  valuable  fact 
relative  to  this  interesting  and  important  subject. 

The  author  wishes  to  acknowledge  indebtedness  to  F.  M. 

Rice,  A.M.,  of  the  Chemical  Department  of  Harvard  Dental 

School  for  reviewing  manuscript. 

H.  C.  S. 


TO   THE   STUDENT. 


As  the  student  of  dentistry  takes  up  the  study  of  chemistry, 
it  is  necessary  that  he  should  realize  that  the  course  will  be  of 
value  to  him  in  the  ability  acquired  to  draw  correct  inferences 
from  observed  phenomena,  and  in  the  attainment  of  accuracy 
and  delicacy  in  manipulation,  fully  as  much  as  in  amount  of 
chemical  knowledge  obtained.  In  other  words,  he  must  do  his 
own  thinking,  carry  out  his  own  processes  and  experiments, 
make  his  own  analyses,  or  the  time  spent  will  be  little  better 
than  wasted,  for  the  chemical  facts  which  he  may  happen  to 
remember  will  be  of  sHght  benefit  in  the  work  to  which  every 
student,  worthy  of  the  name,  aspires,  that  of  developing, 
broadening,  and  elevating  the  profession  which  he  has  chosen 
as  his  own. 

The  course  of  study  outhned  in  this  book  is  designed  to 
furnish  the  starting-points,  which  will  be  of  practical  value  in 
solving  the  problems  constantly  presenting  themselves  for  con- 
sideration in  the  various  branches  of  chemistry.  It  is  hoped 
that  these  starting-points  may,  in  the  future,  serve  as  the  basis 
for  work  along  the  Hnes  of  original  research  and  that  the  best 
interests  of  dental  science  may  be  furthered  thereby. 

It  is  supposed  that  the  student  has  had  the  advantage  of  a 
laboratory  training  in  general  chemistry  and  is  conversant 
with  the  properties  and  methods  of  preparation  of  the  so-called 
non-metallic  elements,  also  with  the  fundamental  principles 
and  laws  of  theoretical  and  physical  chemistry,  that  he  is 
familiar  with  laboratory  apparatus,  such  as  test-tubes,  beakers, 
crucibles,  casseroles,  evapora ting-dishes,  retorts,  etc.,  and  that 


Vi  TO   THE  STUDENT 

he  has  had  some  experience  in  the  ordinary  processes  of  pre- 
cipitation, filtration,  evaporation,  distillation,  subhmation,  and 
crystallization. 

If  there  is  any  feeling  of  insufficient  preparation  it  is  strongly 
advised  that  a  short  course  of  preliminary  study  be  taken. 
Chemistry  furnishes  the  groundwork  of  all  branches  of  medical 
science  to  a  much  greater  extent  than  we  are  apt  to  think, 
and  even  in  the  study  of  subjects  which  in  times  past  have 
been  carried  on  with  little  reference  to  chemistry,  we  now  see 
the  desirabiHty  if  not  the  necessity  of  a  good  general  knowl- 
edge of  chemical  science.  The  physiologist  and  the  bacteriolo- 
gist are  to-day  turning  to  chemistry  for  the  utlimate  solution 
of  their  most  perplexing  problems. 

H.  C.  S. 


TABLE   OF   CONTENTS. 


Page 

Title  Page : i 

Preface  to  First  Edition iii 

Preface  to  Second  Edition v 

To  THE  Student vi 

PART   I. 
QUALITATIVE  ANALYSIS. 

Chapter 

I.  Introduction i 

II.   Metals  and  Their  Salts ii 

III.  Metals  of  Group  One 14 

Analysis  of  Group  One 19 

IV.  Metals  of  Group  Two 21 

Special  Tests  for  Arsenic 28 

Analysis  of  Group  Two    ' 37 

V.  Metals  of  Group  Thrjee 43 

Analysis  of  Group  Three 47 

VI.   Metals  of  Group  Four 51 

Analysis  of  Group  Four 55 

VII.  Metals  of  Group  Five 59 

Analysis  of  Group  Five 64 

VIII.   Metals  of  Group  Six 69 

Outline  Scheme  for  Analysis 82 

IX.    AN.ALYTICAL   REACTIONS   OF   THE   ACIDS 85 

X.  Analysis  in  the  Dry  Way 96 

PART   II. 
DENTAL  METALLURGY. 

XL   Properties  of  the  Metals 105 

XII.  Alloys 108 

XIII.  Amalgams 112 

XIV.  Dental  Cements 120 

XV.  Fusible  Metals  and  Solders 126 

XVI.   Recovery  of  Residue 133 

vii 


Viii  TABLE  OF  CONTENTS 

PART  III. 

VOLUMETRIC  ANALYSIS. 

Chapter  Page 

XVII.   Standard  Solutions 137 

Quantitative  Analysis  of  Dental  Alloys 157 

PART  IV. 

MICROCHEMICAL  ANALYSIS. 

XVIII.   Methods 159 

XIX.  Local  Anesthetics 164 

XX.  Teeth  and  Tartar 178 

PART  V. 

ORGANIC  CHEMISTRY. 

XXI.  The  Hydrocarbons  and  Substitution  Products 181 

XXII.  Alcohols 195 

XXIII.  Ethers 204 

XXIV.  Organic  Acms 212 

XXV.  Amins  or  Substituted  Ammonias 226 

XXVI.   Cyanogen  Compounds 228 

XXVII.   Urea 232 

XXVIII.   Closed-chain  Hydrocarbons 240 

PART   VI. 

PHYSIOLOGICAL   CHEMISTRY. 

XXIX.   Ferments  or  Enzymes 253 

XXX.   Carbohydrates 258 

XXXI.   Fats  and  Oils 267 

XXXII.   Proteins 270 

Simple  Proteins 278 

Conjugated  Proteins 285 

Derived  Proteins 291 

Blood  and  Muscle   294 

PART  VII. 
DIGESTION. 

XXXIII.  Properties  and  Constituents  of  Saliva 302 

XXXIV.  Analysis  of  Saliva 314 

Crystals  from  Dialyzed  Saliva 326 

Tests  for  Abnormal  Constituents 329 


TABLE  OF  CONTENTS  ix 

Chapter  Page 

XXXV.   Gastric  Digestion 331 

XXXVI.  Pancreatic  Digestion  and  Bile 337 

PART   VIII. 
URINE. 

XXXVII.  Physical  Properties  of  Urine 343 

XXXVIII.   Normal  Constituents 348 

XXXIX.  Abnormal  Constituents 358 

Urinary  Sediments 367 

Interpretation  of  Results 372 

Appendix , 377 


DENTAL   CHEMISTRY 


PART    I. 

SALTS   OF   THE   METALS   AND   QUALITATIVE  ANALYSIS 


CHAPTER   I. 
INTRODUCTION. 

Every  science  has  a  language  peculiar  to  itself,  a  thorough 
understanding  of  which  is  an  essential  preHminary  to  the  study 
of  that  science.  Hence,  before  we  take  up  the  study  of  Dental 
Chemistry,  it  will  be  well  to  review  a  few  definitions  and  per- 
haps a  few  of  the  facts  of  Physics  which  are  closely  related  to 
our  subject. 

Elements.  —  An  element  is  one  of  the  simplest  forms  of 
matter  —  a  substance  which  cannot  by  any  means  be  resolved 
into  matter  differing  from  itself. 

Compounds.  —  Compounds  consist  of  two  or  more  elements 
chemically  combined. 

Molecule.  —  The  molecule  is  the  smallest  particle  of  matter 
that  can  exist  and  retain  the  properties  of  the  original  sub- 
stance. 

Atoms.  —  Atoms  are  the  smaller  particles  of  matter  of  which 
molecules  are  composed. 

Statements  regarding  the  size  and  shape  of  atoms  or  mole- 
cules are  statements  of  theories,  which  are  helpful  in  under- 
standing certain  chemical  phenomena  and  some  of  which  will 
be  briefly  considered  in  a  subsequent  lecture. 


2        SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Chemical  Affinity  or  Chemism  is  the  attraction  existing  be- 
tween atoms  whereby  they  are  held  together  as  molecules. 

Valence.  —  Valence  is  a  property  of  atoms  and  represents 
their  combining  power  relative  to  hydrogen.  Valence  is  not 
always  constant  for  the  same  elements;  for  example,  sulphur 
has  a  combining  power  of  six  in  sulphuric  acid,  of  four  in  sulphur 
dioxide,  and  of  two  in  hydrogen  sulphide.  Nitrogen  has  a  com- 
bining power  of  three  in  ammonia  gas  and  five  in  ammonium 
chloride.  Valence  is  also  indicated  by  the  terms  quanti valence 
and  atomicity. 

Bond.  —  The  bond  is  used  to  indicate  the  relationship  of 
atoms  in  a  molecule  and  at  the  same  time  shows  the  valence  of 
the  atom. 

Example,  H  —  O  —  H,  the  dash  (bond)  shows  that  oxygen 
has  two  combining  points  relative  to  the  hydrogen  which  is 
considered  to  have  one. 

Symbols.  —  Symbols  are  used  to  designate  the  various  ele- 
ments. In  some  cases  the  initial  letter  of  the  element  alone  is 
used,  as  C  for  carbon.  In  other  cases  there  is  added  a  dis- 
tinctive small  letter  of  the  name  when  there  happen  to  be  a 
number  of  elements  with  names  beginning  with  the  same  letter 
such  as  Calcium,  Ca;  Cobalt,  Co;  Copper,  Cu;  etc. 

Chemical  Formula.  —  A  chemical  formula  represents  the 
molecule  and  is  made  up  of  the  symbols  of  the  several  con- 
stituent elements.  Chemical  formulae  may  be  empirical,  dua- 
listic  or  graphic.  The  empirical  formula  represents  the  molecule 
without  reference  in  any  way  to  its  structure,  i.e.,  H2SO4. 

The  dualistic  formula  indicates  compounds  which  may  enter 
into  the  composition  of  a  molecule.  By  this  sort  of  formula 
sulphuric  acid  would  be  represented  by  H2O.SO3. 

The  graphic  formula  attempts  to  show  the  probable  relation 
of  the  atoms  in  the  molecule  by  means  of  bonds,  e.g., 


INTRODUCTION  3 

Ions.  —  The  electrically  charged  particles  or  parts  of  mole- 
cules capable  of  attraction  to  either  cathode  or  anode  in  the 
process  of  electrolysis  have  been  called  "  ions "  (Faraday's 
definition).  Ions  may  consist  of  single  atoms  as  in  H+Cl"  or 
of  groups  of  atoms  (radicals)  as  in  water  H+(OH)~  or  ammo- 
nium hydrate  (NH4)+(0H)~. 

Acid.  —  An  acid  is  a  compound  containing  positive  hydro- 
gen ions  which  may  be  replaced  by  a  metallic  element  or  radical. 
The  more  common  acids  are  sour  to  the  taste  and  act  in  char- 
acteristic manner  upon  a  number  of  color  compounds  known  as 
indicators. 

Base.  —  A  base  is  a  substance  containing  negative  hydroxyl 
ions  which  may  be  replaced  by  acid  radicals.  Bases  in  general 
characteristics  oppose  acids.  The  strongest  bases  are  known  as 
alkahes,  e.g.,  KOH,  NaOH. 

A  Salt.  —  A  salt  is  a  substance  produced  by  the  chemical 
union  of  an  acid  and  a  base. 

In  the  formation  of  the  salt  the  acid  may  not  have  been 
completely  neutralized  by  the  base  and  an  acid  salt  results. 
In  such  a  case  the  salt  contains  a  part  of  the  hydrogen  ions  of 
the  acid,  e.g.,  potassium  acid  sulphate,  KHSO4,  the  production 
of  which  may  be  represented  by  the  equation 

KOH  +  H2SO4  =  KHSO4  +  H2O. 

Acid  salts  may  or  may  not  have  acid  properties  such  as  sour 
taste  and  power  to  give  acid  reactions  with  indicators.  A  salt 
may  on  the  other  hand  be  basic  and  contain  a  portion  of  the 
hydroxyl  ions  (or  sometimes  oxygen  atoms)  of  the  base. 

Example:  Bi(0H)3  +  2  HNO3  =  BiOH(N03)2  +  2  H2O    or 
BiCla  +  H2O  =  BiOCl  +  2  HCl. 

If  the  acid  is  exactly  neutralized  by  the  base,  neutral  salts  result. 
2  NaOH  +  H2SO4  =  Na2S04  +  2  H2O. 


4        SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Reactions  between  chemical  substances  may  be  "  completed  " 
or  "  reversible," 

A  completed  reaction  is  one  which  progresses  in  a  definite 
way  irrespective  of  changes  in  temperature  or  of  the  quan- 
tities of  the  reacting  substances;  or,  a  completed  reaction  is 
one  in  which  one  of  the  products  is  chemically  inactive.  This 
inactivity  may  be  due  to  one  of  several  causes,  such  as  the  pro- 
duction of  an  insoluble  precipitate;  e.g.  AgCl  in  the  reaction, 
AgNOsH-  NaCl  =  AgCl  -f  NaNOg, 

or  the  escape  of  the  product  as  a  gas  and  its  consequent  re- 
moval from  solution  —  as  when  carbonates  are  dissolved  by  acid. 
The  reversible  reaction  is  one  in  which  the  products  remain 
to  a  greater  or  less  degree  in  solution  and  a  change  of  temper- 
ature or  increase  in  quantity  of  one  of  the  products  may  start  a 
reverse  reaction;  for  example,  at  the  body  temperature,  dibasic 
sodium  phosphate  and  uric  acid  may  become  monobasic  sodium 
phosphate  and  acid  sodium  urate, 

Na2HP04  -f  H2U  =  NaH2P04  +  NaHU, 
while  at  reduced  temperature, 

NaH2P04  -I-  NaHU  =  Na2HP04  +  H2U.     (See  page  237.) 

Reversible  reactions  are  often  expressed  by  use  of  the  sign 
^■,  thus,  MgCl2  +  2  NH4OH  ^  Mg(0H)2  +  2  NH4CI.  The 
reaction  may  be  expressed  as  an  equation  if  we  know  what  sub- 
stances take  part  in  the  reaction  and  what  products  are  formed. 
The  above  reaction  can  be  balanced  at  a  glance  and  is  therefore 
not  well  suited  for  illustration  but  the  use  of  a  little  more  com- 
plex equation  will  show  how  easily  it  can  be  balanced  by  a  few 
algebraic  combinations. 

Cu  +  HNO3  =  Cu(N03)2  +  NO  -F  H2O. 

Represent  these  all  as  unknown  quantities. 

xCu  +  y HNO3  =  z Cu(N03)2  -\-mNO+p H2O, 
then 


INTRODUCTION 


xCm  =  zCVi 
3;  H    =  ^  H2 

3;  N    =  z  (N)2  +  w  N 
yO^   =  z{0^)2  +  mO+pO 


X  =  z  (i) 

^^      y  =   2p  (2) 

>;   =   2  Z  +  W  (3) 

2,y  =  6z  -{-  m  -\-  p  (4) 


multiplying  equation  3  by  3,  33;  =  6z  +  3W  (5) 

and  by  elimination  (4  and  5)  2m  =  p  (6) 

and  4m  =  2  p,  then  by  eq.  2  y  =  4m  (7) 

assuming  that  w  =  i,  then,  in  7,  3^  =  4;  in  6,  ^  =  2;  in  3,  2  z  =  3, 
orz=i|,  ini,a:  =  i|.  Knowing  that  all  equations  must  be 
expressed  by  whole  numbers  we  double  these  values  and  have 
^  =  S^y  =  8,z  =  3,w  =  2,^  =  4. 

Upon  substituting  these  values  we  shall  find  that  the  equa- 
tion "  balances." 

Solution.  —  If  we  are  to  study  physiological  chemistry  a 
clear  understanding  of  the  meaning  of  this  term  is  desirable. 

"  Solution  is  the  equal  distribution  of  a  body  in  a  liquid, 
the  resulting  mass  being  in  all  parts  homogeneous  and  fluid 
enough  to  form  drops,"  according  to  an  old  definition  quoted 
in  "  Colloids  and  the  Ultra-microscope  "  by  Dr.  Richard  Zsig- 
mondy. 

We  can  readily  adopt  this  definition  for  present  use  pro- 
vided our  conception  of  homogeneity  is  sufficiently  elastic  to 
include  "  Colloidal "  solutions,  which  as  a  class  are  of  rapidly 
increasing  importance. 

The  colloids  are  distinguished  from  crystalloids  by  their  in- 
ability to  pass  through  parchment  membrane.  In  colloidal 
solutions  the  substance  (colloid)  may  be  considered  as  in 
suspension  or  a  state  of  subdivision  so  nearly  complete  as 
to  approach  closely  to  the  homogeneity  of  crystalloidal  solu- 
tion. 

In  many  colloidal  solutions  the  particles  are  large  enough  to 
interfere  with  the  passage  of  light  and  the  preparation  is  more 
or  less  opaque.  In  some,  however,  this  is  not  noticeable  except 
by  use  of  polarized  light  and  special  apparatus. 


6       SALTS  OF  THE  METALS  AND  QUALITATIVE  ANALYSIS 

There  is  no  sharply  defined  hne  between  the  suspensions  and 
the  colloidal  solutions,  and  it  is  often  true  that  the  homogeneity 
of  a  solution  is  dependent  upon  the  "  grossness  of  our  means  of 
observation."  The  separation  of  the  solid  particles  from  the 
liquid  may  be  effected  in  several  ways. 

Sedimentation  serves  to  remove  the  coarser  particles  from 
suspension:  the  liquid  in  this  case  may  be  decanted  or  turned 
off  from  the  heavy  sediment. 

Filtration  through  paper  will  remove  the  finer  particles  of 
suspension  or  ordinary  precipitates. 

Some  very  fine  precipitates,  such  as  sulphur  and  barium  sul- 
phate, require  special  papers. 

Colloidal  substances  as  a  class  may  be  separated  from  the 
crystalloids  by  Dialysis,  animal  membrane  suspended  in  dis- 
tilled water  being  used  as  a  separating  medium.  The  crystal- 
loids will  pass  through  the  membrane  into  the  pure  water,  while 
the  colloids  remain  behind.  The  use  of  the  dialyzer  as  applied 
to  saliva  analysis  is  shown  on  page  327. 

Osmosis  signifies  the  passage  of  water  only  through  a  mem- 
brane, tending  to  correct  inequalities  of  pressure  produced  by 
differences  in  molecular  concentrations  of  two  solutions. 

This  is  usually  illustrated  by  dropping  potassium  ferro- 
cyanide  solution  into  copper  sulphate.  The  drop  of  potassium 
ferrocyanide  becomes  surrounded  by  a  film  of  copper  ferro- 
cyanide,  through  which  water  alone  will  pass.  Membrane  of 
this  character  is  known  as  semi-permeable. 

Porous  cups  are  prepared  for  demonstrations  of  osmosis  by 
precipitating  within  the  pores  of  the  cup  or  cell  the  ferrocyanide 
of  copper. 

Osmotic  pressure  is  the  pressure  produced  within  a  semi- 
permeable cell  by  passage  of  water  from  the  outside;  or,  as 
stated  by  Holland,  it  is  "  That  push  of  the  molecules  of  a  solute 
upon  its  solvent  which  causes  a  flow  through  a  membrane  into 
the  solution." 


INTRODUCTION  7 

Measures.  —  The  metric  system  of  weights  and  measures 
and  the  centigrade  thermometer  are  largely  used  in  all  scien- 
tific work.  The  dentist,  however,  has  also  considerable  use 
for  troy  weights  and  apothecaries'  measures  if  he  considers  at 
all  the  composition  of  his  gold  solders,  dental  alloys,  mouth 
washes,  local  anaesthetics,  etc.  Hence,  a  few  equivalents  are 
here  given. 

The  metre  is  the  primary  unit  of  the  metric  system  and  was 
originally  calculated  as  one  ten-millionth  part  of  the  quadrant 
from  the  equator  to  the  pole. 

I  metre  =  loo  centimeters  =  looo  millimeters  or  39.37 
inches. 

I  centimeter  =  10/25  or  0.3937  of  an  inch. 

I  cubic  centimeter  =  16.23  minims  or  0.0338  of  a  fluid  ounce. 

1000  cubic  centimeters  (c.c.)  i  liter  or  2. 113  pts. 

The  weight  of  i  c.c.  of  pure  water  at  the  temperature  of  its 
greatest  density  (4°  C.)  is  taken  as  a  unit  of  weight  and  called 
a  gram  (gramme). 

I  gram  =  15 -43  grains. 

1000  grams  =  i  kilogram  (kilo)  =35  oz.  120  grains  or 
2.2  lbs.  avoir. 

I  inch  =  2.54  centimeters  or  25.4  millimeters. 

I  oz.  av.  =  28.3495  grams  or  437.5  grains. 

I  fluid  oz.  =  8  fluid  drams,  29.57  c.c,  or  456  grains  of  water. 

I  fluid  dram  =  3.7  c.c. 

I  troy  oz.  =  8  drams  (5)  or  480  grains. 

I  troy  oz.  =  24  scruples  (3)  or  20  pennyweight  (pwt. 
or  dwt.) 

I  scruple  =  20  grains,  i  penn3;'weight  =  24  grains, 

I  grain  =  64  milligrams. 

I  pint  =  473.11  c.c. 

I  gallon  =  8  pints,  or  3785  c.c,  or  231  cubic  inches. 

I  lb.  avoir.  =  7000  grains  or  453.59  grams. 


8        SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Measure  of  Temperature.  —  We  shall  constantly  meet  ref- 
erence to  both  the  Centigrade  and  Fahrenheit  scales  and  an 
understanding  of  the  relationship  of  the  two  methods  is 
essential. 

The  thermometer  is  graduated  by  marking  the  point  at 
which  the  mercury  stands  when  the  instrument  is  placed  on 
melting  ice;  and  again  the  point  reached  by  the  mercury  when 
the  thermometer  is  surrounded  by  dry  steam  under  ordinary 
atmospheric  conditions. 

On  the  Centigrade  thermometer,  the  lower  or  freezing  point 
is  marked  o,  the  upper  or  boiling  point  is  marked  loo,  and  the 
intervening  space  divided  into  loo  equal  degrees.  On  the 
Fahrenheit  scale,  these  points  are  marked  respectively  32  and 
212  and  the  scale  is  divided  into  180°;  hence,  1°  C.  equals  1.8° 
or  9/5°  Fahrenheit,  and  1°  F.  equals  5/9  of  a  Centigrade  degree. 
Providing  for  the  different  freezing  points  (0°  and  32°),  we  can 
formulate  a  rule  for  converting  temperature  records  from  one 
scale  to  the  other,  as  follows: 

To  convert  Centigrade  to  Fahrenheit,  take  9/5  of  the  given 
number  of  degrees  and  add  32. 

To  convert  Fahrenheit  to  Centigrade,  subtract  32  from  the 
given  number  and  take  5/9  of  the  remainder;  e.g. 

20°  C.  =  68°  F. 
-5°C.  =+23°F. 
77°  F.  =  25°  C. 
14°  F.  =-io°C. 

Absolute  Temperature. 

According  to  the  Law  of  Charles  or  of  Gay-Lussac,  gases 
(free  molecules)  contract  1/273  of  their  volume,  measured  at 
0°  C,  for  every  Centigrade  degree  that  the  temperature  falls; 
so  it  is  assumed  that,  at  a  point  273°  below  the  Centigrade  zero, 
no  further  contraction  would  be  possible,  molecular    motion 


INTRODUCTION  9 

would  cease  and  all  things  become  solid.  This  temperature 
has  been  called  the  absolute  zero  and  temperature  recorded 
from  this  point  absolute  temperature;  thus,  water  freezes  at 
273°  C.  absolute  temperature. 

Gravity  Signifies  Weight. 

Specific  gravity  is  the  relative  weight  of  equal  bulks  of 
different  substances,  one  of  which  is  taken  as  a  standard. 

The  standard  is  usually  water  for  hquids  and  solids. 

The  standard  for  gases  may  be  air  or  hydrogen. 

When  gases  are  referred  to  hydrogen  as  a  standard,  the  term 
density  is  often  used  instead  of  specific  gravity,  and,  to  avoid 
confusion,  this  usage  is  recommended;  i.e.,  the  density  of  carbon 
dioxide  is  22,  while  its  specific  gravity  compared  with  air  is 
about  1.53. 

The  density  of  a  gas  will,  according  to  the  Law  of  Avogadro,, 
be  one-half  its  molecular  weight. 

The  specific  gravity  of  a  liquid  may  be  diminished  by  the 
solution  of  a  gas,  as  in  case  of  solution  of  ammonia;  or  it  may 
be  increased,  as  in  case  of  solution  of  hydrochloric  acid.  Specific 
gravity  is  increased  by  solution  of  solid  substances. 

The  boiling  point  of  a  liquid  is  raised  by  the  solution  of 
solids. 

The  freezing  point  of  water  is  lowered  by  solution  of  either 
solids  or  gases. 

Cryoscopy  is  a  term  applied  to  the  determination  of  freezing 
points  in  their  relations  to  conditions  of  concentration  or  of 
purity.  In  medicine,  the  body  fluids,  such  as  blood,  milk,  and 
urine,  have  been  investigated  in  this  way. 

Precipitation  signifies  throwing  out  in  solid  form  a  substance 
previously  held  in  solution. 

Precipitation  may  be  brought  about  in  three  ways: 

First,  by  change  of  temperature,  many  substances  being  solu- 
ble at  high  temperature  which  will  precipitate  as  the  solution  cools. 


lO     SALTS  OF   THE  METALS  AND  QUALITATIVE   ANALYSIS 

Second,  by  change  in  the  character  of  the  solvent;  example, 
laboratory  exercise  i,  experiments  i  and  2. 

These  two  may  be  regarded  as  physical  methods,  while  the 
third  is  chemical  and  involves  the  production  of  a  new  and 
comparatively  insoluble  substance:  example,  laboratory  exer- 
cise I,  experiments  5  and  7. 

An  old  law  of  precipitation  is,  in  effect,  as  follows:  whenever 
two  substances  in  solution  can,  by  an  interchange  of  radicals, 
produce  a  soluble  and  an  insoluble,  or  a  soluble  and  a  less  solu- 
ble substance,  double  decomposition  always  takes  place  and  the 
less  soluble  substance  will  be  precipitated. 

Laboratory  Exercise  I. 

Conditions  Influencing  Precipitation. 

Write  Reactions  if  possible. 

Exp,  I.  Mix  equal  volumes  of  an  alcoholic  solution  of 
camphor  and  water.     Explain  precipitation. 

Exp.  2.  To  concentrated  HCl  add  a  saturated  solution  of 
NaCl.     Explain  precipitation. 

Exp.  3.  To  2  c.c.  of  HgCl2  solution,  found  on  side  shelf,  add 
2  c.c.  of  KI  solution. 

Exp.  4.  To  2  c.c.  of  HgCl2  used  above  add  5  c.c.  of  KI  solu- 
tion. 

Exp.  5.  To  a  mixture  of  CUSO4  and  CdS04  add  H2S  water 
and  filter.  To  the  filtrate  add  more  H2S  water  and  filter  again 
if  precipitate  forms.  Repeat  till  no  further  precipitation  takes 
place. 

Exp.  6.  To  a  few  cubic  centimeters  of  strong  HCl  add  one 
drop  of  AgNOs  solution. 

Exp.  7.  To  a  few  cubic  centimeters  of  dilute  HCl  add  one 
drop  of  AgNOs  solution. 

Exp.  8.     Mix  strong  HNO3  and  H2S  water. 

Exp.  9.     Mix  (NH4)2Sx  solution  and  HCl  concentrated. 


CHAPTER  II. 
THE   METALS  AND   THEIR  SALTS. 

Qualitative  Analysis. 

The  metals  occur  free  in  nature  to  quite  an  extent,  but  more 
often  combined  with  other  elements.  These  combinations  are 
chiefly  as  oxids,  sulphids,  carbonates,  and  silicates,  and  in  one 
or  more  of  these  four  forms  the  great  mass  of  metals  contained 
in  the  earth's  crust  may  be  found. 

Metallic  sulphates  are  found  to  a  considerable  extent. 

Other  natural  sources  of  the  metals  are  phosphates  and 
chlorids,  also  smaller  amounts  of  nitrates  and  comparatively 
slight  amounts  of  bromids,  iodids,  and  fluorids.  Metals  are 
extracted  from  their  ores  chiefly  by  reduction  with  some  form 
of  carbon.  In  case  of  the  oxids  this  reduction  takes  place  directly, 
according  to  this  reaction:    2  CuO  +  C  =  2  Cu  +  CO2. 

In  case  the  metallic  combination  is  a  sulphid,  the  ore  is  first 
"roasted"  in  the  air,  whereby  the  sulphur  is  burned  off  and  an 
oxid,  which  may  then  be  reduced  as  above,  is  formed: 
2  CuS  +  3  O2  =  2  CuO  +  2  SO2. 

The  native  carbonates  are  reduced  to  oxids  by  calcination,  as 
CaCOs  +  heat  =  CaO  +  CO2. 

The  silicates  must  first  be  changed  to  carbonates  by  fusion 
with  alkali  carbonates ;  then  the  reduction  may  be  carried  on  as 
before : 

MgSiOs  +  Na2C03  =  MgCOa  +  Na2Si03; 

then  MgCOs  +  heat  =  MgO  +  CO2. 

The  metals,  from  certain  physical  properties,  have  been  van- 


12     SALTS  OF   THE   METALS  AND  QUALITATIVE  ANALYSIS 

ously  classified.  Thus,  in  the  older  books  we  read  of  the  Noble 
metals,  those  unaffected  by  heat,  as  gold,  silver,  and  platinum; 
the  Base  metals,  the  Bastard  metals,  those  easily  crystalhzable, 
as  antimony  and  zinc;   the  Metalloids,  sodium  and  potassium. 

As  the  fact  that  the  properties  of  metals  were  to  a  con- 
siderable extent  dependent  upon  conditions  of  temperature  and 
pressure  became  better  understood,  the  old  classifications  were 
less  and  less  used,  until  now  we  are  very  apt  to  group  them 
according  to  the  chemical  behavior  of  their  salts,  irrespective 
of  their  properties  as  metals.  Thus  Ag,  Pb,  and  Hg  (Mercur- 
ous)  form  a  group  of  metals  whose  chlorids  are  insoluble  in 
water  or  dilute  acids.  These  metals  may  consequently  be 
thrown  out  of  solution  or  precipitated  by  the  addition  of  HCl 
to  any  solution  of  their  salts.  We  therefore  let  Ag,  Hg',  and 
Pb  constitute  the  First  Analytical  Group,  and  HCl  is  the  First 
Group  Reagent. 

In  like  manner  we  find  a  group  of  nine  metals  that  are  pre- 
cipitated from  dilute  acid  solution  by  hydrosulphuric  acid 
(H2S).  These  metals  are  Cu,  Cd,  Bi,  Hg,  As,  Sb,  Sn,  Au,  and 
Pt,  and  constitute  the  Second  Analytical  Group,  and  H2S  is  the 
Second  Group  Reagent. 

The  fact  that  the  sulphids  formed  by  the  first  four  of  these 
metals  are  insoluble  in  ammonium  sulphid,  and  those  formed  by 
the  last  five  are  soluble,  furnishes  a  simple  method  of  separat- 
ing this  group  into  two  parts,  a  and  b : 

Pb,*  Cu,  Cd,  Bi,  and  Hg  constituting  Group  II  (a)  and 

As,  Sb,  Sn,  Au,  and  Pt,  Group  II  (b). 

Thus,  the  metals  are  divided  into  various  analytical  groups, 
each  with  its  own  peculiar  group  reagent.  Different  groupings 
are  possible,  and  hardly  any  two  analysts  will  employ  exactly 
the  same  scheme  for  identifying  all  the  metals,  although  the 
following  group  divisions  are  generally  used: 

*  Lead  is  included  in  this  group  because  it  is  not  entirely  separated  as  a  chlorid 
in  Group  I,  traces  of  it  remaining  in  solution  even  after  addition  of  HCl. 


THE  METALS  AND   THEIR  SALTS  13 

Analytical  Groups. 

Group  I.  —  Ag,  Pb,  and  Hg'.  Metals  that  form  insoluble 
chlorids  and  are  precipitated  from  aqueous  solution  by 
HCl  (the  group  reagent). 

Group  II  (a).  — Cu,  Cd,  Bi,  Hg'',  and  Pb.  Metals  that  form 
sulphids  insoluble  in  dilute  HCl  solution  and  also  insoluble 
in  ammonium  sulphid. 

Group  II  {h).  — As,  Sb,  Sn,  Au,  and  Pt.  Metals  that  form 
sulphids  insoluble  in  dilute  HCl  but  soluble  in  yellow- 
ammonium  sulphid,  or  alkaline  hydrates. 

Group  III.  —  Fe,  Al,  and  Cr.  In  solutions  free  from  H2S 
and  which  do  not  contain  phosphates,  oxalates,  tartrates, 
or  salts  of  certain  other  organic  acids  these  three  metals 
may  be  separated  by  ammonium  hydrate,  (NH4OH). 

Group  IV.  —  Co,  Ni,  Mn,  and  Zn.  Metals  forming  sulphids 
soluble  in  acid  but  insoluble  in  alkaHne  solution.  Ammo- 
nium sulphid,  (NH4)2S,  is  the  group  reagent. 

Group  V.  —  Ba,  Sr,  Ca,  and  Mg.*  Metals  forming  car- 
bonates, insoluble  in  alkaline  solutions.  The  group 
reagent  is  ammonium  carbonate,  (NH4)2C03. 

Group  VI.  —  K,  Na,  Li,  NH4. .  Metals  which  cannot  be 
precipitated  by  any  single  reagent  and  for  which  it  is 
necessary  to  make  individual  tests. 

It  is  our  purpose  to  take  up  the  study  of  the  metals  accord- 
ing to  their  analytical  grouping:  first,  the  deportment  of  their 
salts  in  solution;  later,  the  metals  themselves  and  their  specific 
application  to  dentistry. 

*  In  the  process  of  analysis,  magnesium  is  held  in  solution  by  the  presence  of 
NH4CI  and  is  not  thrown  out  as  a  carbonate  with  the  other  three  members  of 
the  group. 


CHAPTER  III. 
METALS   OF   GROUP  I. 

Silver,  Ag  (Argentum). 

The  Metal. — Atomic  weight  107.93.  Silver  occurs  free,  as 
sulphids,  such  as  silver  glance,  Ag2S,  and  in  combination  with 
the  sulphids  of  antimony,  lead,  and  copper. 

It  occurs  also  as  silver  chlorid,  AgCl,  known  as  "Horn 
Silver." 

Silver  fuses  at  954°  C,  forming  a  revolving  globule  on  char- 
coal or  plaster  without  oxidation. 

Silver  dissolves  in  hot  H2SO4  with  evolution  of  SO2.  It  is 
readily  soluble  in  nitric  acid  with  formation  of  AgNOs,  colorless 
crystals,  without  water  of  crystalHzation. 

Silver  amalgamates  readily,  and  the  "amalgamation  process" 
is  one  of  the  important  methods  for  its  reduction  from  the  ore. 

This  process,  briefly,  is  as  follows:  The  ore  is  roasted  with 
salt,  producing  chlorid  of  silver;  this,  in  suspension  in  water,  is 
reduced  by  metallic  iron, 

2  AgCl  +  Fe  =  FeCla  +  2  Ag. 

The  mixture  treated  with  mercury  forms  an  amalgam  from 
which  the  mercury  can  be  driven  off  by  heat. 

Alloys.  —  Important  alloys  of  silver  are  United  States  coin 
silver,  consisting  of  silver  90  parts,  copper  10  parts;  and  Sterling 
silver  consists  of  silver  92.5  parts,  copper  7.5  parts.  Dental 
or  amalgam  alloys  contain  50  to  65%  silver. 

Compounds.  —  Salts  of  silver  are  liable  to  decomposition  by 
action  of  hght  with  reduction  in  greater  or  less  degree  to  metallic 

14 


METALS  OF  GROUP  I.  1$ 

silver.  The  salts  change  from  violet  to  black  according  to  the 
amount  of  silver  reduced.  Such  reduction  is  used  in  the  prep- 
aration and  use  of  the  ordinary  photographic  plates. 

Silver  oxid  (Ag20),  a  dark  brown  powder,  may  be  produced 
in  the  wet  way,  i.e.,  by  precipitation  of  soluble  silver  salts  with 
hydroxids  of  the  fixed  alkalis. 

2  AgNOa  +  2  NaOH  =  AgaO  +  H2O  +  2  NaNOg. 

Silver  hydroxid  (white)  may  be  formed  if  the  above  reaction 
is  brought  about  in  alcohohc  solution;  but  it  is  a  very  unstable 
compound,  quickly  changing  to  Ag20  +  H2O.  Silver  thiosul- 
phate,  Ag2S203,  may  be  precipitated  white  from  solution  of  silver 
nitrate  and  sodium  thiosulphate.  Excess  of  the  thiosulphate 
produces  a  soluble  double  salt  NaAgS203.  This  fact  may  be 
utilized  in  the  removal  of  silver  stains. 

Fused  silver  nitrate  in  the  form  of  pencils  or  small  sticks  is 
used  as  an  escharotic,  and  is  known  as  "Lunar  Caustic. "  Dilute 
lunar  caustic  consists  of  equal  parts  of  AgNOs  and  KNO3  fused 
together  in  pencil  form. 

Analytical  Reactions.  —  Make  the  following  tests  with  a 
weak  solution  of  AgNOs  (about  2%).  Write  the  reactions  and 
enter  color  and  solubility  of  each  precipitate  formed  in  labora- 
tory note-book.* 

AgNOa  with  HCl  gives  a  white  curdy  precipitate  of  AgCl 
which  darkens  by  action  of  sunlight.  If  Ag  solution  is  very 
dilute,  the  precipitate  will  assume  the  curdy  appearance  and 
filter  more  easily  if  it  is  heated  and  rotated  quite  rapidly  in 
the  test-tube.  Allow  the  precipitate  to  settle.  Decant  the 
liquid  carefully,  divide  precipitate  into  two  parts,  and  test  its 
solubihty  in  dilute  nitric  acid,  also  in  ammonia  water. 

*  The  author  uses  mimeograph  copies  of  these  experiments  with  space  for  the 
reactions  and  colors  of  precipitates,  which  are  filled  out  without  reference  to  the 
book  and  handed  in  by  the  student  at  the  close  of  the  laboratory  exercise. 

These  reactions  have  purposely  been  confined  to  such  as  may  be  applied  to  the 
process  of  analysis. 


l6     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

AgNOs  with  KBr  gives  a  white  precipitate  of  AgBr,  less 
easily  soluble  in  ammonia  than  the  AgCl. 

AgNOs  with  KI  gives  a  pale  yellow  precipitate  of  Agl, 
insoluble  in  ammonia. 

AgNOs  with  H2S  gives  a  black  precipitate  of  Ag2S.  AgNOa 
with  K2Cr04  gives  a  red  precipitate  of  Ag2Cr04  in  neutral  solu- 
tion. Test  the  solubility  of  Ag2Cr04  in  NH4OH,  HCl,  and 
HNO3. 

Mercury,  Hg  (Hydrargyrum). 

The  Metal.  — Atomic  weight  199.8.  Occurs  as  red  sulphid, 
cinnabar,  and  in  small  quantities  amalgam.ated  with  silver  or 
gold  or  combined  with  chlorin  or  iodin.  It  is  the  only  metal 
which   is   liquid    at   ordinary    temperatures,    solidifying    at  — 

39°  C. 

It  boils  at  357-8°  C.  and  this  wide  range  of  temperature 
throughout  which  the  fluid  form  is  maintained,  together  with  its 
coiliparatively  great  coefficient  of  expansion  (about  1/160), 
makes  it  particularly  suitable  for  use  in  thermometers  and  other 
instruments  for  measuring  temperature  or  pressure. 

The  molecule  of  mercury  consists  of  a  single  atom. 

Alloys  of  mercury  are  amalgams  and  will  be  considered 
under  this  head. 

Compounds.  —  Mercury  forms  two  series  of  salts;  one,  mer- 
curous  salts  referable  to  the  oxide  Hg20,  in  which  mercury 
exhibits  a  valence  of  one;  and  the  other,  mercuric,  referable  to 
HgO,  the  mercury  having  a  valence  of  two. 

(Mercuric  compounds  will  be  considered  under  group  two.) 

Mercurous  chloride,  or  calomel,  may  be  made  by  the  reduc- 
tion of  HgCl2  by  a  reducing  agent,  as  SO2.  2  HgCl2  +  2  H2O  -|- 
SO2  =  2  HgCl  -f  H2SO4  -|-  2  HCl;  but  the  process  commercially 
employed  is  usually  to  sublime  a  mixture  of  mercuric  sulphate, 
sodium  chloride  and  mercury. 

HgS04  +  2  NaCl  +  Hg  =  2  HgCl  +  NaaSOi. 


METALS  OF  GROUP  I.  1 7 

Mercurous  iodide,  Hgl,  is  a  greenish  colored  unstable  salt 
produced  by  double  decomposition  of  HgNOs  and  KI. 

Mercurous  nitrate  is  an  easily  soluble  salt  produced  by 
action  of  cold  nitric  acid  on  excess  of  mercury,  a  solution  of 
which  may  be  used  for  the  study  of  mercurous  precipitates. 

Note.  —  The  solution  of  mercurous  nitrate,  upon  standing,  will  be  found  to 
contain  more  or  less  mercuric  nitrate,  unless  care  is  taken  to  keep  excess  of  mer- 
cury in  the  bottom  of  the  bottle. 

Analytical  Reactions.  —  HgNOa  with  HCl  gives  a  white  pre- 
cipitate of  HgCl  (calomel).  After  the  precipitate  has  settled, 
decant  the  liquid,  and  test  the  solubility  of  the  HgCl  in  ammonia 
water.  Does  it  dissolve?  How  does  its  behavior  differ  from 
that  of  AgCl? 

Alkaline  hydroxids  form  with  mercurous  salts  the  black  oxid 
Hg20;  a  preparation  of  which,  made  with  lime-water  and  calo- 
mel, is  known  as  "blackwash. " 

Lead,  Pb  (Plumbum). 

The  Metal.  —  Atomic  weight  206.9.  Melting-point  from 
325°  to  335°  C.  Occurs  as  sulphid  (galena),  PbS,  in  lesser  quan- 
tities as  native  carbonate  (cerussite),  also  as  phosphate  and 
chromate. 

Lead  is  reduced  from  the  sulphid  in  a  reverberatory  furnace 
by  a  few  simple  reactions  as  follows :  3  PbS  -f  5  O2  =  2  PbO  -f 
PbS04  +  2  SO2;  then,  by  increasing  the  heat  without  access  of 
air,  the  sulphur  is  driven  off  and  the  lead  separates  by  two  double 
decompositions, 

2  PbO  -f-  PbS  =  3  Pb  +  SO2  and  PbSOi  +  PbS  =  2  Pb  -f  2  SO2. 

Lead  is  soluble  in  nitric  or  acetic  acid,  forming  Pb(N03)2  or 

Pb(C2H302)2. 

Lead  is  also  dissolved  to  a  very  slight  extent  by  pure  water 
containing  oxygen,  or  by  water  containing  CO2,  mineral  salts 


l8     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

or  organic  matter.  It  tarnishes  in  the  air,  with  formation  of  a 
suboxide,  Pb20. 

Alloys.  — •  Solders  and  fusible  metals  are  among  the  important 
alloys. 

Type  metal  consists  of  an  alloy  of  lead  and  antimony. 

Compounds.  —  Besides  the  suboxide  of  lead  above  mentioned, 
three  more  compounds  of  lead  and  oxygen  are  of  interest. 

Litharge,  PbO,  is  the  yellow  oxide  used  in  pharmacy  as  the 
base  of  "Diacylon  plaster. " 

The  black  oxide,  PbOa,  is  used  as  an  oxidizing  agent.  Red 
lead' (minium),  Pb304,  is  practically  a  mixture  of  Pb02  and  2  PbO, 
and  used  as  a  source  of  Pb02  by  treatment  with  HNO3. 

Pb304  +  4  HNO3  =  Pb02  +  2  Pb(N03)2  +  2  H2O. 

Lead  carbonate,  as  prepared  by  precipitation  of  soluble  lead 
salts  by  alkali  carbonates,  has  the  composition  (PbC03)2Pb(OH)2. 

The  basic  carbonate,  prepared  by  exposure  of  the  metal  to 
fumes  of  acetic  acid,  CO2,  and  moisture,  is  known  as  ''White 
lead, "  and  is  used  in  manufacture  of  paint. 

Lead  acetate,  or  sugar  of  lead,  formed  by  solution  of  the 
metal  or  the  oxide  PbO  in  acetic  acid,  is  a  white  soluble  salt 
crystallizing  with  three  molecules  of  H2O.  The  solution  has  an 
acid  reaction  to  litmus  paper. 

Lead  subacetate,  or  basic  acetate  of  lead,  a  solution  of  which 
is  known  as  Goulard's  extract,  is  made  by  boiling  lead  acetate 
solution  with  litharge.  It  is  used  in  medicine  as  an  external  ap- 
plication and  in  physiological  chemistry  as  a  reagent.  It  deteri- 
orates by  absorption  of  CO2  and  precipitation  of  a  carbonate. 

Lead  chromate  (chrome  yellow)  is  a  yellow  insoluble  salt 
used  as  a  pigment. 

Lead  nitrate,  an  easily  soluble  white  crystalline  salt,  may 
be  used  in  the  study  of  the  analytical  reactions  of  lead. 

Lead  arsenate,  a  poisonous  salt,  is  quite  largely  used  for 
spraying  trees. 


METALS  OF  GROUP  I. 


19 


Analytical  Reactions.  —  Pb(N03)2  with  2  HCl  gives  white 
precipitate  of  PbCl2.  Test  its  solubility  in  hot  water  and  in 
NH4OH. 

Pb(N03)2  with  NH4OH  gives  white  precipitate  of  Pb(0H)2 
insoluble  in  hot  water. 

Pb(N03)2  with  H2S  gives  black  PbS.  Test  solubihty  of 
precipitate  in  warm  dilute  HNO3. 

Pb(N03)2  with  H2SO4  gives  white  precipitate  of  PbS04,  form- 
ing slowly  in  dilute  solutions. 

Pb(N03)2  with  K2Cr04  (or  K2Cr207)  gives  a  yellow  pre- 
cipitate of  PbCr04. 

Pb(N03)2  gives  with  KI  a  yellow  precipitate,  Pbl2.  Avoid 
excess  of  the  potassium  iodid. 

By  application  of  the  reactions  of  the  salts  of  Ag,  Pb,  and 
Hg',  we  may  formulate  a  scheme  for  the  separation  and  identi- 
fication of  the  metals  of  Group  I  as  follows: 

Analysis  of  Group  I. 

(Ag,  Pb,  Hg'.) 

To  the  clear  solution  to  be  tested  add  slowly  dilute  HCl  as 
long  as  any  precipitation  occurs.  Filter  and  wash  the  precipi- 
tate once  with  cold  water,  add  this  washing  to  filtrate  to  be 
tested  for  remaining  groups,  then  wash  precipitate  on  the  paper 
with  several  small  portions  of  hot  water. 


AgCl  and  HgCl  remain  undissolved. 


PbCl2  is  in  the  hot-water  solution. 


Divide  this  hot-water  solution  into  three  parts  and  make 
three  of  the  following  tests  for  lead:  First,  with  K2Cr207,  which 


20     SALTS  OF  THE  METALS  AND  QUALITATIVE  ANALYSIS 

gives  yellow  precipitate  of  PbCr04.  Second,  with  dilute  H2SO4, 
giving  a  white  precipitate  of  PbS04.  Third,  with  H2S  water, 
giving  black  precipitate  of  PbS.  Fourth,  with  KI  solution,  which 
forms  a  yellow  precipitate  of  Pbl2.     Write  these  reactions. 

To  undissolved  residues  of  Hg  and  Ag  chlorids  add  warm 
NH4OH. 

Hg  remains  on  the  paper,  black,  as  HgNH2HgCl. 

Ag  is  dissolved  by  the  NH4OH  and  may  be  precipitated 
as  AgCl  by  adding  HNO3  to  acid  reaction.  Presence  of 
Hg  in  the  black  residue  may  be  confirmed  as  in  Group  II 
(page  38). 

QUESTIONS  ON  GROUP  I. 

Why  wash  the  precipitated  chlorids  only  once  with  cold 
water  ? 

Why  is  it  necessary  to  wash  the  PbCla  out  with  hot  water 
before  using  ammonia? 

Why  is  the  ammonia  used  ? 

How  does  HNO3  reprecipitate  silver  chlorid? 

Laboratory  Exercises  II  and  III. 

Laboratory  exercises  2  and  3  will  consist  of  the  analytical 
reactions  of  the  first-group  metals,  a  study  of  the  solubility  of 
the  precipitates  formed,  and  an  analysis  of  an  unknown  solu- 
tion containing  a  mixture  of  first-group  metals. 


CHAPTER  IV. 
METALS   OF   GROUP   II. 

Copper,  Cu  (Cuprum). 

The  Metal. — Atomic  weight  63.3.  Melting-point  1054°  C. 
Occurs  free  in  vicinity  of  Lake  Superior,  also  in  western  United 
States,  Chili,  and  Spain,  as  sulphids,  copper  pyrites,  CuFeS2,  and 
copper  glance,  CU2S.  Malachite  green  and  malachite  blue  are 
native  basic  carbonates  of  Cu. 

Copper  dissolves  easily  in  nitric  acid  and  with  difficulty  in 
HCl;  heated  with  H2SO4  it  forms  CUSO4,  with  the  evolution  of 
SO2. 

Alloys  of  Copper  are  both  numerous  and  important.  The 
amalgam  was  formerly  used  in  dentistry  to  a  considerable 
extent. 

Copper  is  used  to  harden  silver  and  gold,  used  in  the  manu- 
facture of  coins,  jewelry  and  the  solders,  and  used  in  crown  and 
bridge  work. 

Copper  is  also  used  in  the  preparation  of  bronze,  brass,  bell 
metal,  dental  gold,  and  German  silver.     Page  108. 

Compounds.  —  Salts  and  solutions  of  copper  are  usually 
blue  or  green. 

Copper  forms  two  series  of  salts :  the  cuprous,  of  which  there 
are  but  few  important  compounds,  and  the  cupric.  Cuprous 
oxid,  CU2O,  which  is  red  in  color  (sometimes  yellow  through 
admixture  of  CuOH)  and  obtained  by  reduction  of  cupric  salts 
by  organic  substances  such  as  sugar,  and  cuprous  chlorid,  used 
as  a  reagent  for  the  detection  of  acetylene,  are  perhaps  the  most 
important. 


22     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Cupric  oxid,  CuO,  is  a  black  powder  formed  by  ignition  of 
copper  in  the  air  or  by  boiling  copper  solution  with  the  fixed 
alkali  hydroxids. 

Copper  arsenate  and  aceto-arsenite,  the  latter  known  as 
Paris  green,  are  both  green  powders  which  have  been  used  as 
pigments  and  as  insecticides. 

Copper  sulphate,  CUSO4,  crystallizes  with  five  molecules  of 
water  and  is  known  as  blues  tone  or  blue  vitriol.  It  is  used 
extensively  in  the  "Gravity  Battery,"  and  in  copper  plating. 

Verdigris  is  a  sub-acetate  or  oxy-acetate  of  copper  composi- 
tion, CU20(C2H302)2. 

Copper  salts  combine  with  NH3,  forming  a  series  of  "cupram- 
monium"  compounds  freely  soluble  and  of  intense  blue  color. 

The  chlorid  nitrate  and  sulphate  are  the  common  soluble 
salts.  A  1%  solution  of  either  of  these  will  give  the  analytical 
reactions. 

Analytical  Reactions.  —  CUSO4  with  H2S  gives  CuS,  brownish- 
black  sulphid.  Test  its  solubility  in  (NH4)2S  and  in  warm  dilute 
HNO3. 

CUSO4  with  NH4OH  (one  or  two  drops  of  -reagent)  will  pre- 
cipitate Cu(0H)2  bluish  white.  Add  more  NH4OH  to  same  test- 
tube  and  note  the  result.  To  this  clear  solution  add  a  sufficient 
amount  of  dry  KCN  to  completely  decolorize  the  liquid.  Then 
add  to  the  mixture  some  H2S  water.  Is  the  black  CuS  thrown 
out?  The  behavior  of  Cu  solutions  thus  treated  is  due  to  the 
formation  of  double  salts,  the  solution  in  ammonia  being  due 
to  a  compound  of  CUSO4  and  NH3,  and  the  decolorization  of  the 
blue  solution  to  one  of  Cu(CN)2  and  KCN. 

CUSO4  with  K4FeCy6  (potassium  ferrocyanid)  gives  in  acetic 
acid  solution  a  red-brown  precipitate  of  Cu2FeCy6. 

Metallic  zinc  or  iron  will  precipitate  copper  from  solution. 
Hold  a  knife-blade  in  a  solution  of  CUSO4  for  a  few  seconds. 


METALS  OF  GROUP  II.  23 

Mercury  in  Mercuric  Combination. 

Compounds  of  Dyad  Mercury.  —  Mercuric  oxid,  HgO,  is  a 
red  powder  obtained  by  ignition  of  mercury  in  the  air.  Mer- 
curic oxid  may  also  be  prepared  by  precipitation  of  mercuric 
chlorid  with  alkaline  hydroxids.  A  precipitate  thus  formed  is 
yellow  in  color,  and,  when  prepared  by  mixing  mercuric  chlorid 
and  lime  water,  forms  the  "yellow  wash"  used  to  a  considerable 
extent  in  pharmacy. 

Mercuric  chlorid,  HgCl2.  This  intensely  poisonous  salt  is 
known  by  the  fairly  descriptive  name  of  corrosive  sublimate. 
It  corrodes  metals,  such  as  zinc  and  iron;  it  coagulates  albumin 
and  acts  as  a  corrosive  poison  when  taken  internally. 

It  is  made  in  a  manner  analogous  to  that  used  for  the  prepar- 
ation of  calomel,  i.e.,  by  sublimation,  the  salts  used  in  this 
instance  being  mercuric  sulphate  and  sodium  chlorid  alone. 

Hg2S04  +  NaCl  =  2  HgCl  4-  Na2S04. 

Mercuric  chlorid  is  antiseptic  and  a  disinfectant  in  dilu- 
tions of  I  to  1000.  Antiseptic  tablets  designed  to  give  about 
this  strength  of  solution  by  the  addition  of  one  tablet  to  one 
pint  of  water  are  made  to  contain  7.7  grains  HgCU  and  7.3 
grains  NH4CI,  with  sufficient  purple  coloring  to  advertise  the 
nature  of  the  tablets  and  thus  act  as  a  safeguard  against  acciden- 
tal poisoning. 

Mercuric  chlorid  is  soluble  in  water  and  in  alcohol.  It  is 
used  in  the  preparation  of  antiseptic  gauze,  sterile  cotton,  etc., 
but,  on  account  of  its  corrosive  properties,  cannot  be  used  to 
sterilize  instruments. 

Ammoniated  mercury,  mercur-ammonium  chlorid,  or  white 
precipitate  (NH2HgCl)  is  a  white  powder  obtained  by  slowly 
pouring  a  solution  of  HgCl2  into  ammonia  water. 

Mercuric  iodid,  red  iodid  (Hgl2),  is  made  by  reaction  of 
mercuric  chlorid  with  potassium  iodid: 

HgCl2  +  2  KI  =  2  KCl  +  HgL 


24     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Mercuric  iodid  is  soluble  in  excess  of  either  reagent,  also  in 
alcohol. 

Mercuric  iodid  combines  with  potassium  iodid  (KI)  form- 
ing an  iodo-hydrargyrate,  used  as  a  reagent  in  physiological 
chemistry  (page  278),  also  as  an  alkaloidal  precipitant. 

An  alkaline  solution  of  potassium  iodo-hydrargyrate,  con- 
stitutes Nessler's  reagent,  used  in  analysis  of  water  and  of  saliva 
as  a  test  for  ammonium  compounds. 

Analytical  Reactions. — A  2%  solution  of  corrosive  sub- 
limate (HgCl2)  may  be  used  in  demonstrating  the  reactions  of 
dyad  mercury. 

HgCl2  with  H2S  gives  first  a  white  precipitate,  turning  yellow, 
brown,  and  finally  black,  as  proportion  of  H2S  increases.  The 
black  precipitate  only  is  mercuric  sulphid,  and  care  must  be 
taken  to  add  H2S  till  this  compound  is  produced. 

Test  the  solubiHty  of  HgS  in  (NH4)2S  and  HNO3. 

To  HgCl2  solution  add  SnCl2.  The  mercuric  chlorid  is  re- 
duced to  mercurous  chlorid  (HgCl,  white)  or  metallic  mercury 
(Hg,  gray),  according  to  proportion  of  the  tin  salt  used: 

2  HgCl2  +  SnCl2  =  2  HgCl  +  SnCU 
or  HgCl2  4-  SnCl2  =  Hg -h  SnCl4. 

HgCl2  with  KI  gives  red  Hgl2,  easily  soluble  in  excess  of 
either  of  the  reagents. 

HgCl2  with  NH4OH  gives  white  precipitate  of  (NH2Hg)Cl, 
known  as  "white  precipitate"  (see  ammoniated  mercury). 
"Red  precipitate"  is  a  term  sometimes  used  to  designate  the 
red  oxid  of  mercury,  HgO,  made  in  the  dry  way. 

Bismuth,  Bi. 

The  Metal. — Atomic  weight  208.5;  melting-point  268°  C. 
At  higher  temperatures  Bi  burns  to  Bi203.  Bismuth  does  not 
occur  in  large  quantities,  but  is  usually  found  in  the  free  state. 


METALS   OF  GROUP  II. 


25 


Small    amounts  are    obtained  from    the  oxid,  Bi203,  bismuth 
ochre,  and  from  the  sulphid,  61283. 

It  is  easily  identified  by  means  of  the  blowpipe  test  on 
plaster  with  S  and  KI  (page  102). 

Alloys.  —  The  most  important  alloys  from  a  dental  stand- 
point are  the  fusible  metals,  Mellot's  metal,  Wood's  metal, 
Rose's  metal,  etc.  (page  126). 

Compounds,  —  Salts  of  bismuth  as  a  rule  require  excess  of 
acid  for  permanent  solution;  and,  by  adding  a  considerable 
volume  of  water,  they  are  easily  thrown  out  of  solution  as  insol- 
uble basic  or  oxysalts,  the  reaction  of  the  nitrate  being  as 
follows : 

Bi(N03)3  +  H2O  =  BiON03  +  2  HNO3. 

This  may  be  demonstrated  by  allowing  a  few  drops  of  bis- 
muth solution  to  fall  into  a  comparatively  large  amount  of  H2O 
(two  to  six  ounces).  A  white  cloud  of  insoluble  oxysalt  may 
be  observed  settling  through  the  clear  water.  This  may  be  em- 
ployed as  a  final  test  for  Bi  in  the  course  of  systematic  analysis. 

The  subnitrate  and  the  subcarbonate  of  bismuth  are  both 
used  in  medicine.  The  latter  is  a  common  starting-point  in  the 
preparation  of  other  bismuth  salts. 

Analytical  Reactions.  —  The  most  available  salt  is  the 
nitrate,  insoluble  in  water  unless  strongly  acidulated. 

Use  a  2%  solution  of  Bi(N03)3  in  the  following  tests: 

Bi(N03)3  with  NH4OH  gives  white  precipitate  of  bismuth 
hydroxid,  Bi(0H)3. 

Bi(N03)3  with  H2S  precipitates  Bi2S3,  brownish  black,  in- 
soluble in  (NH4)2S,  but  soluble  in  warm  dilute  HNO3. 

Cadmium,  Cd. 
The  Metal. — Atomic  weight  112.4;   melting-point  320°  C. 
Occurs  associated  with  Zn  in  zinc  blende.     It  is  more  easily 
volatile  than  zinc,  and  advantage  is  taken  of  this  fact  in  effect- 
ing its  separation  from  that  metal. 


26     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Alloys.  —  Cadmium  is  used  as  a  constituent  of  fusible 
metals  and  rarely,  in  small  proportion,  in  dental  alloys.  Its  use 
in  the  latter  case  is  objectionable  on  account  of  the  yellow  stain 
of  CdS  frequently  produced  (page  115,  amalgam). 

Analytical  Reactions. — A  2%  solution  of  the  sulphate  or 
nitrate  may  be  used  in  studying  the  deportment  of  cadmium 
salts. 

CdS04  with  H2S  gives  a  bright  yellow  sulphid,  CdS,  soluble 
in  dilute  nitric  acid. 

CdS04  with  (NH4)2S  also  precipitates  the  yellow  sulphid. 

Cadmium  sulphid  forms  slowly,  and,  in  presence  of  Cu  or 
other  second-group  metals,  may  escape  precipitation  if  the 
reagent  is  added  in  insufficient  quantity. 

Arsenic,  As. 

Atomic  weight  75.0.  Occurs  associated  with  copper  and 
iron  sulphids,  as  arsenical  pyrites,  FeAs.FeS2;  as  native  sulphids, 
orpiment,  AS2S3,  and  realgar,  AS2S2;  also  to  some  extent  as  the 
trioxid,  AS2O3. 

Compounds.  —  Arsenic  forms  two  series  of  salts,  the  arseni- 
ous.  As'",  and  arsenic,  As",  and  it  also  acts  as  an  acid  radical 
forming  arsenious  and  arsenic  acids.  In  the  process  of  analysis, 
arsenic  compounds  whether  acid  or  basic  are  reduced  to  arseni- 
ous by  action  of  H2S.  It  is  most  easily  obtained  in  the  form 
of  the  trioxid,  AS2O3,  also  known  as  arsenious  acid  or  white 
arsenic. 

White  arsenic  is  intensely  poisonous;  but,  nevertheless,  it 
has  been  very  freely  used  in  curing  the  skin  of  fur-bearing 
animals  and  otherwise  as  a  preservative.  In  dentistry  white 
arsenic  is  used  to  devitalize  pulp. 

Arsenic  is  widely  distributed  in  nature,  occurring  in  soft  coal, 
from  which  source  it  finds  its  way  into  the  roadside  dust  or 
any  substance  capable  of  holding  dust,  such  as  the  majority  of 
fabrics,  wall  papers,   etc.     Arsenic  is  a  common  impurity  in 


METALS  OF  GROUP  II.  27 

mercury,  zinc,  and  commercial  acids.  Inasmuch  as  these  things 
are  largely  used  in  the  preparation  of  filHng  material  used  by 
dentists,  it  is  necessary  that  considerable  pains  be  taken  to 
prevent  the  presence  of  the  poison  in  sufficient  quantity  to 
cause  irritation. 

The  poisonous  character  of  arsenic  differs  greatly  with  the 
combination  in  which  it  occurs.  A  gaseous  hydrid  of  arsenic, 
AsHs,  being  among  the  most  poisonous  of  its  compounds,  while 
some  of  the  organic  compounds  are  claimed  to  be  non-poisonous. 

Arsenic  forms  an  insoluble  arsenate  with  ferric  hydrate; 
hence,  freshly  precipitated  ferric  hydroxid  is  the  official  anti- 
dote for  arsenical  poisoning.  This  is  prepared  by  mixing  150  c.c. 
of  dilute  ferric  sulphate  solution  (containing  50  c.c.  of  the  U.  S.  P. 
"Solution")  with  a  well-shaken  mixture  of  10  grains  of  oxid 
of  magnesium  in  about  750  c.c.  of  water: 

Fe2(S04)3  +  3  Mg(0H)2  =  Fe2(OH)6  +  3  MgS04. 

Fowler's  solution  containing  1%  AS2O3  dissolved  by  use  of 
potassium  bicarbonate.  Solution  of  arsenious  acid  containing 
1%  AS2O3  dissolved  by  aid  of  two  parts  of  HCl.  Donovan's 
solution  containing  1%  each  of  Asis  and  Hgl2,  and  Pearson's 
solution  containing  1%  sodium  arsenate  are  Pharmacopoeial 
preparations  of  arsenic. 

Analytical  Reactions.  —  A  solution  for  studying  the  reactions 
of  arsenic  (As'")  is  conveniently  made  by  dissolving  about 
15  grams  of  white  arsenic  in  dilute  NaOH  solution  by  aid  of 
heat,  then  diluting  to  one  liter  and  acidifying  slightly  with 
HCl. 

To  an  arsenious  solution,  which  may  be  represented  by  AsCls, 
add  H2S  water.  A  lemon-yellow  precipitate  of  AS2S3  will  be 
thrown  down.  Test  the  solubility  of  this  precipitate  in  yellow 
ammonium  sulphid  and  in  ammonium  carbonate. 

To  the  alkahne  solution  of  the  sulphid  add  excess  of  HCl: 
AS2S3  is  precipitated. 


.28     SALTS  OF   THE   METALS  AND  QUALITATIVE  ANALYSIS 

To  an  arsenious  solution  add  (NH4)2S  in  repeated  small 
portions. 

In  neutral  solution,  as  of  sodium  arsenite,  NasAsOs,  silver 
nitrate  will  throw  down  yellow  silver  arsenite,  soluble  in  excess 
of  nitric  acid  or  ammonia. 

SPECIAL   TESTS   FOR  ARSENIC. 

Reinsch's  Test  for  arsenic,  applicable  to  any  solution 
whether  organic  or  not,  and  very  valuable  for  a  preliminary  test, 
is  made  as  follows:  place  the  solution  or  mixture  to  be  tested 
in  a  porcelain  dish,  acidify  strongly  with  HCl,  and  add  a  small 
strip  of  bright  copper  foil  (cleaned  in  dilute  HNO3  and  thor- 
oughly washed  in  distilled  H2O)  and  boil  for  ten  or  twenty 
minutes,  adding  sufficient  water  to  replace  loss  by  evaporation. 
Remove  the  copper  foil ;  a  dark  gray  to  black  coating  is  an  indi- 
cation of  arsenic  but  not  conclusive,  as  some  other  substances 
give  similar  deposits,  mercury  and  antimony  in  particular. 

To  prove  the  presence  of  As  roll  the  foil  as  tightly  as  possible 
and  place  it  in  the  bulb  of  a  small  glass  matrass  (Fig.  i). 


Fig.  I. 

Heat  the  bulb  over  a  very  small  luminous  flame,  when  crys- 
tals of  AS2O3  (tetrahedral  or  octahedral)  will  deposit  in  the  con- 
stricted portion  of  the  tube,  and  which  may  be  identified  by 
microscopical  examination.  There  will  be  sufficient  air  in  the 
matrass  for  the  formation  of  the  oxid  and  the  test  becomes  much 
more  dehcate  than  if  heated  in  the  ordinary  open  tube  as  often 
recommended. 

Gutzeit's  Test  is  made  by  placing  the  suspected  solution 
in  a  test-tube,  acidifying  with  H2SO4,  adding  a  few  small  pieces 
of  arsenic-free  zinc,  and,  as  hydrogen  begins  to  be  given  off, 
placing  over  the  mouth  of  the  tube  a  piece  of  filter-paper  carry- 


METALS  OF  GROUP  II.  29 

ing  a  drop  of  a  strong  solution  of  AgNOa-  The  presence  of 
arsenic  is  indicated  by  the  darkening  of  the  moistened  filter- 
paper  in  accordance  with  the  following  reactions: 

The  nascent  H  liberated  by  action  of  the  Zn  upon  the  acid 
forms  with  any  As  present  the  gaseous  AsHs  which,  in  contact 
with  the  filter-paper  wet  with  AgNOs  solution,  produces  a  brown 
or  black  stain  of  metallic  Ag,  while  the  As  becomes  arsenious 
acid,  H3ASO3.  The  stain  may  possibly  be  yellow  by  forma- 
tion of  a  compound  of  silver  arsenide  and  silver  nitrate,  but,  as  a 
rule,  moisture  is  present  in  sufficient  amount  to  insure  the  decom- 
position of  this  compound. 

Antimony  will  give  a  similar  brown  or  black  stain  (not 
yellow),  but  presence  of  As  may  be  conclusively  demonstrated 
by  making  Fleitmann's  Test,  which  is  conducted  in  the  same 
way  as  the  preceding,  except  that  the  hydrogen  is  evolved  in 
alkaline  solution,  either  by  means  of  Zn  and  strong  KOH  solu- 
tion (Zn  -|-  2  KOH  =  K2Zn02  +  H2)  or  by  sodium  amalgam 
(made  with  arsenic-free  mercury)  and  water  (NaHg^  -j-  H2O  = 
NaOH  -f-  Hg  4-  H) .  In  this  case  the  SbHs  is  not  formed;  so  a 
stain  thus  obtained  constitutes  a  positive  test  for  arsenic. 

The  Marsh-Berzelius  Test  for  arsenic  is  the  most  deHcate 
of  all  and  the  one  to  which  we  resort  in  detecting  As  in  the  saliva 
or  the  urine.  By  this  method  one  two-hundredth  of  a  milligram 
or  about  1/ 12800  of  a  grain  can  be  easily  shown  as  a  brown 
deposit  in  the  constricted  tube  at  about  the  point  K,  Fig.  2. 
The  apparatus  used  in  this  test  is  shown  in  Fig.  2,  and  consists 
of  a  small  Erlenmeyer  flask,  or  wide-mouth  bottle,  fitted  as  a 
hydrogen  generator.  A,  and  connected  with  a  drying-tube,  B, 
filled  with  fused  calcium  chlorid,  then  with  a  tube  of  hard  glass, 
C,  drawn  out  to  a  very  small  diameter  for  half  its  length. 

The  generator  A  is  charged  with  arsenic-free  zinc,  and  dilute 
sulphuric  acid  (1/5)  introduced  through  the  thistle-tube  E. 
After  all  air  has  been  driven  from  the  apparatus,  light  the  escaping 
H  at  r,  then  the  Bunsen  burner  D,  and  allow  the  generator  to 


30     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

run  for  about  twenty  minutes,  thus  making  a  blank  test  of 
apparatus  and  reagents;  if  at  the  end  of  this  time  the  hard  glass 
is  perfectly  free  from  any  deposit,  the  suspected  liquid,  which 
must  have  been  freed  from  organic  matter  (process  described 
in  detail  in  chapter  on  Urine  Analysis),  may  be  introduced  in 
portions  of  about  lo  c.c.  each. 

The  flame  should  be  spread  somewhat  so  as  to  heat  at  least 
I  inch  of  the  glass  tube.     This  may  be  accomplished,  in  the 


^T 


Fig.  2. 

absence  of  a  burner-tip,  by  placing  an  inverted  V-shaped  piece 
of  asbestos  board,  i  inch  wide,  over  the  heated  part  of  the  tube. 

The  presence  of  arsenic  increases  the  evolution  of  hydrogen 
and,  unless  the  solution  is  added  gradually,  the  AsHa  may  be 
driven  so  rapidly  past  the  flame  as  to  escape  decomposition,  or 
the  tube  may  become  heated  to  such  an  extent  that  arsenic  will 
not  be  deposited. 

The  escape  of  As  at  T  may  be  noticed  by  the  bluish  color  of 
the  flame  and  by  the  characteristic  garlic  odor. 

Antimony  is  similarly  deposited  as  a  dead-black  stain  in- 
stead of  brown-black,  and  as  Sb  is  less  easily  volatile  than  As 


METALS  OF  GROUP  II.  3 1 

the  deposit  will  be  nearer  the  flame,  possibly  on  both  sides  of 
the  flame.  (For  further  differences  between  As  and  Sb  see 
tests  given  on  page  32.) 

A  test,  using  an  apparatus  similar  to  the  above  and  known 
as  Gutzeit's  test,  has  been  investigated  by  Sanger  and  Black, 
(proceedings  of  the  American  Academy  of  Arts  and  Sciences, 
October,  1907). 

AsHs  is  produced  in  the  generator  by  use  of  Zn  and  HCl, 
and  passed  through  the  drying  tube  B\  (Fig.  2)  then  through 
a  tube  of  uniform  diameter  C  containing  strips  of  drawing  paper 
sensitized  with  solution  of  PIgCl2. 

The  HgCl2  paper  is  stained  yellow  to  brown  beginning  at 
the  end  next  the  generator,  and  by  carefully  regulating  con- 
ditions, the  extent  of  the  stain  may  have  a  quantitative  value. 

Arsenic  compounds  (As"),  as  Na2HAs04,  are  of  but  Httle 
interest  from  the  dentist's  standpoint. 

All  arsenic  compounds,  are  reduced  by  nascent  H  to  arsenious 
combinations,  then  to  elementary  As,  then  to  AsHs  (arsine); 
hence  the  special  tests  given  for  arsenious  compounds  are  ap- 
plicable. 

Free  chlorin,  nitric  acid,  and  potassium  ferricyanid  oxidize 
arsenious  compounds  to  arsenic,  and  in  this  condition  the  As 
is  not  easily  volatihzed  and  organic  matter  may  be  destroyed 
by  deflagration  (in  presence  of  excess  of  nitrates)  with  but 
slight  loss  of  arsenic. 

Antimony,  Sb  (Stibium). 

Atomic  weight  120.2.  Occurs  native  in  Australia,  and  as 
the  sulphid,  Sb2S3,  known  as  stibnite. 

Alloys.  —  Antimony  is  used  in  making  type  metal,  Britan- 
nia metal,  and  rarely  in  low-grade  dental  alloys. 

Compounds.  —  The  salts  of  antimony  may  be  classified  as 
antimony  salts,  referable  to  the  hydroxid  Sb(0H)3,  and  anti- 
monyl  salts,  referable  to  SbO(OH)3. 


32     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 


Butter  of  antimony,  antimony  tri-chlorid,  SbCls,  when 
pure,  is  a  colorless  solid  of  buttery  consistency,  hence  its 
name.  It  may  be  formed  by  direct  union  of  constituent 
elements. 

Salts  of  antimony  tend  to  form  oxycompounds  and  are  held 
in  solution  by  excess  of  acid.  The  antimonious  chlorid,  SbCla, 
in  solution  with  HCl  is  precipitated  by  excess  of  water  as  a 
white  oxychlorid,  Sb4Cl205,  also  known  as  "powder  of  Algaroth." 
The  antimonic  chlorid  in  like  manner  precipitates  the  anti- 
monic  oxychlorid,  SbOCla.  Demonstrate  by  turning  i  or  2  c.c. 
of  SbCla  solution  into  a  large  excess  of  water. 

Analytical  Reactions.  —  The  most  common  compound  of 
antimony  is  the  double  tartrate  of  antimony  and  potassium 
(KSbOC4H406),  known  as  tartar  emetic  (an  antimonyl  com- 
pound). A  2%  aqueous  solution  may  be  used  in  the  following 
tests : 

To  an  antimony  solution  represented  by  SbCls   add  H2S 
water:    ^hSz  is  precipitated  orange-red.     Test  solubility  of  the 
precipitate  in  (NH4)2S  and  in  (NH4)2C03. 
How  does  it  differ  from  arsenic  ? 

Upon  the  addition  of  HCl  in  excess  to  the 
ammonium  sulphid  solution  the  Sb  is  repre- 
cipitated,  but  not  necessarily  as  Sb2S3,  but 
more  usually  as  Sb2S5  or  a  mixture  of  the 
two  sulphids. 

Marsh's  test  for  As  (or  Sb)  consists  of  a 
simple  hydrogen  generator  with  glass  tip  for 
burning  the  gas,  as  shown  in  Fig.  3.  In  this 
apparatus  Sb  and  As  are  converted  into  the 
gaseous  hydrides,  AsHs  and  SbHs;  and,  if  a 
piece  of  cold  porcelain  is  pressed  down  upon 
the  flame,  As  or  Sb  will  be  deposited  as 
metalHc  stains  (mirrors)  upon  the  porcelain.  To  distinguish  be- 
tween As  and  Sb  spots  the  following  tests  will  suffice: 


Fig.  3. 


METALS  OF   GROUP  II.  33 

Arsenic.  Antimony. 

Brown-black,  lustrous  spots.  Dead  brown  or  black  surfaces. 

Soluble  in  solution  of  hypo-  Insoluble  in  solution  of  hypo- 
chlorite of  lime  or  soda.  chlorite  of  lime  or  soda. 

Easily  volatilized.  Volatilized  at  red  heat. 

Antimony  may  be  retained  in  the  generator  by  the  intro- 
duction of  a  piece  of  platinum-foil,  the  Sb  being  precipitated 
upon  the  platinum  to  which  it  adheres  quite  strongly. 

Tin,  Sn  (Stannum). 

The  Metal. — Atomic  weight  119.0;  melting-point  238°  C. 
Cassiterite,  or  tin-stone,  nearly  pure  Sn02,  is  by  far  the  most 
important  source.  The  free  metal  has  been  found  associated 
with  gold. 

Banca  tin  from  the  East  Indies  and  block  tin  from  England 
are  pure  varieties  of  the  commercial  article.  Pure  tin  will  give 
a  peculiar  crackling  sound  when  bent.  Tin  is  very  malleable  at 
the  ordinary  temperature,  being  fourth  in  the  list  of  malleable 
metals  (see  page  105),  but  becomes  brittle  when  heated  to  about 

o  r^ 
200    L. 

Alloys.  — •  Pewter  usually  contains  Sn,  Pb,  Cu,  and  Sb,  some- 
times Zn.  Rees's  alloy  Sn  20  parts,  gold  i  part,  and  silver  2 
parts.  Tin  is  also  a  constituent  of  solders,  fusible  metals, 
Babbitt's  metal,  bell  metal,  and  bronze. 

An  alloy  of  tin  and  mercury  (tin  amalgam)  is  used  for  "silver- 
ing mirrors." 

Compounds.  —  Metallic  tin  is  not  dissolved  by  HNO3,  but 
is  converted  into  a  white,  insoluble  metastannic  acid.  This 
acid,  upon  standing,  changes  to  normal  stannic  acid  which  is 
easily  soluble  in  acids;  hence,  in  making  use  of  this  reaction  in 
the  analysis  of  amalgam  alloys,  it  is  not  well  to  allow  the  nitric 
acid  solution  of  the  alloy  to  stand  too  long  before  filtering. 


34     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Metallic  zinc  thrown  into  a  tin  solution  will  precipitate  the 
tin  as  follows:   SnCl2  +  Zn  =  ZnCl2  +  Sn. 

This  reaction  is  used  in  the  separation  of  tin  from  antimony 
in  the  second  group;  and,  in  order  to  obtain  the  tin  in  soluble 
form  suitable  for  a  final  test,  it  is  necessary  to  add  HCl  sufficient 
first  to  dissolve  all  the  Zn  present;  otherwise  it  (Sn)  may  remain 
adhering  to  the  zinc. 

Tin,  like  arsenic  and  antimony,  forms  two  series  of  salts,  the 
stannous  (Sn")  and  the  stannic  (Sn^^).  A  Httle  HCl  treated 
with  excess  of  granulated  tin  till  hydrogen  is  no  longer  given  off 
furnishes  a  solution  of  stannous  chlorid  suitable  for  the  follow- 
ing experiments: 

Analytical  Reactions.  —  SnCl2  with  H2S  gives  brown  pre- 
cipitate of  SnS,  soluble  in  (NH4)2S,  insoluble  in  (NH4)2C03. 

SnCl2  with  HgCl2  gives  a  white  or  gray  precipitate,  as  ex- 
plained on  page  24  under  "Mercury,"  and  is  used  as  a  test  for 
presence  of  mercury.  It  may  also  be  used  as  an  alkaloidal  pre- 
cipitant. 

Strong  solutions  of  SnCU  in  presence  of  metallic  Sn  keep 
fairly  well,  but  dilute  solutions  without  an  excess  of  tin  oxidize 
very  rapidly  to  stannic  combinations  and  cease  to  be  of  value 
as  reagents. 

Gold,  Au  (Aurum). 

Atomic  weight  197.2;  melting-point  1075°  C.  Usually  found 
uncombined,  but  mixed  with  various  impurities. 

Alloys.  —  Gold  is  alloyed  with  copper  to  make  it  harder  and 
more  durable  for  use  in  the  manufacture  of  jewelry,  plate,  and 
coin.  It  is  alloyed  with  silver  for  the  purpose  of  reducing  its 
melting  point.  Copper  and  zinc,  or  copper,  silver,  and  zinc  may 
be  used  in  this  way.     (Seepage  130  for  formulae  for  gold  alloys.) 

The  term  "carat"  as  applied  to  gold  signifies  1/24  part  and 
is  used  as  a  measure  of  purity  of  an  alloy,  22  carat  gold  being 
22/24  pure  gold.     Twenty  carat  gold  is  20/24  pure,  etc.     The 


METALS  OF  GROUP  II. 


35 


Fig.  4. 


amount  of  gold  in  a  given  alloy  may  be  determined  approxi- 
mately by  use  of  a  device  shown  in  Fig.  4,  much  used  by 
jewelers,  consisting  of  a  series  of  stand- 
ard alloys  and  a  piece  of  stone  upon 
which  the  test  is  made.  The  tips  are 
standard  alloys.  Parallel  markings  are 
made  on  the  stone  with  the  alloy  in 
question  and  with  the  tip  supposed  to 
correspond  to  it;  then  the  addition  of  a 
drop  of  strong  nitric  acid  to  the  marks 
and  a  careful  comparison  of  their  ap- 
pearance will  show  if  the  two  are  of  the 
same  composition. 

If  the  composition  of  an  alloy  is 
known,  the  value  in  carats  may  be 
determined  by  the  following: 

Rule  to  determine  the  carat  of  a  given  alloy:  Multiply  24 
by  the  weight  of  gold  used  and  divide  result  by  total  weight 
of  alloy.  For  instance,  if  an  alloy  is  made  containing  9  parts 
of  gold  and  3  of  another  metal,  the  total  weight  will  be  12  and 
the  calculations  24  X  9  ^  12  =  18.  The  alloy  is  an  i8-carat 
gold. 

Gold  may  be  raised  to  a  higher  carat  by  the  following  rule: 
Multiply  weight  of  alloy  used  by  difference  between  its  carat 
and  that  of  the  metal  to  be  added.  Then  divide  product  by  the 
difference  between  the  carat  of  the  metal  added  and  that  of  the 
required  alloy.  The  figure  thus  obtained  represents  the  total 
weight  of  required  alloy.  Subtract  from  this  weight  of  material 
taken  and  difference  in  weight  of  pure  or  alloyed  gold  to  be 
added.     (From  Hall's  Dental  Chemistry.) 

To  reduce  gold  to  a  required  carat  Essig  takes  the  following 
rule  from  Richardson's  Mechanical  Dentistry:  "Multiply  the 
weight  of  gold  used  by  24  and  divide  the  product  by  the  required 
carat.     The  quotient  is  the  weight  of  the  mass  when  reduced, 


36     SALTS   OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

from  which  subtract  the  weight  of  the  gold  used,  and  the  re- 
mainder is  the  weight  of  the  alloy  to  be  added." 

Analytical  Reactions.  —  Gold  is  insoluble  in  simple  acids, 
but  may  be  dissolved  in  nitrohydrochloric  acid  (aqua  regia)  with 
formation  of  auric  chlorid.  Gold  also  unites  easily  with  Br  or 
I,  forming  AuBrs  or  Aula.  A  one-half  per  cent  solution  of  AuCls 
may  be  us.ed  in  the  following  tests : 

H2S  with  AuCls  gives  dark  brown  AU2S3  (auric  sulphid), 
soluble  in  yellow  ammonium  sulphid. 

Gold  is  reduced  to  the  metallic  state  by  many  of  the  other 
metals,  as  Pb,  Cu,  Ag,  Sn,  Al,  Sb,  Fe,  Mg,  Zn,  and  Hg;  also 
by  ferrous  sulphate,  stannous  chlorid,  and  oxalic  acid. 

Add  a  freshly  prepared  solution  of  ferrous  sulphate  to  a 
Kttle  acid  solution  of  AuCls-  Gold  is  precipitated  as  follows: 
AuCls  +  3  FeS04  =  Au  +  Fe2(S04)3  +  FeCls- 

Stannous  chlorid  precipitates  from  gold  solution  the  "purple 
of  Cassius,"  consisting  of  a  mixture  of  gold  and  oxid  of  tin  in 
colloidal  forms. 

Gold  is  only  slowly  precipitated  by  oxalic  acid;  but,  as  Pt 
is  not  precipitated  at  all  by  this  reagent,  it  is  possible  to  separ- 
ate Au  and  Pt  in  solution,  as  chlorids,  by  this  means. 

KI  will  give  a  dark-green  precipitate  of  AUI2  provided  the 
KI  is  in  excess;  if  the  gold  is  in  excess,  the  precipitate  is  apt 
to  be  the  yellow  Aul  (aurous  iodid).  In  the  presence  of  a  con- 
siderable excess  of  KI  the  Aula  is  kept  in  solution  as  the  potassio- 
auric  iodid,  KIAuIs.  The  reduction  of  this  double  salt  by 
sodium  thiosulphate  is  made  the  basis  of  the  method  to  determ- 
ine the  quantity  of  Au  in  a  given  alloy,  as  described  in  the 
chapter  on  Volumetric  Analysis. 

Platinum,  Pt. 

Atomic  weight  194.8.  Melting-point  2000°  C.  Platinum 
solubilities  are  similar  to  gold;  aqua  regia  forms  the  chlorid 
PtCU. 


METALS  OF   GROUP  II.  37 

Alloys.  —  Platinum  alloys  quite  easily  with  other  metals, 
particularly  lead;  and  platinum  utensils  may  be  destroyed  by 
heating  in  contact  with  the  compounds  of  metals  easily  reduced. 
Sulphur  and  phosphorus  also  attack  platinum. 

Platinum  90%  and  iridium  10%  give  an  alloy  harder,  more 
brittle,  and  more  resistant  to  chemical  action  than  pure  platinum. 

"Platinum  Color,"  for  coloring  enamel,  is  made,  according 
to  Mitchell's  Dental  Chemistry,  by  precipitating  platinum 
from  a  solution  of  PtCU  by  boiHng  with  KOH  and  grape  sugar; 
then,  grinding  this  finely  divided  platinum  with  feldspar  in  the 
proportion  of  i  part  Pt  to  16  parts  feldspar. 

Analytical  Reactions.  —  PtCU  +  H2S  gives  a  precipitate  of 
sulphid  of  platinum  almost  black,  soluble  in  yellow  ammonium 
sulphid. 

Platinum  solution  with  NH4CI  precipitates  yellow  ammo- 
nium platinic  chlorid,  (NH4)2PtCl6,  crystalline.  Potassium 
chlorid  also  gives  a  yellow  crystalline  precipitate  of  K2PtCl6, 
isomorphous  with  the  ammonium  compound.  (Plate  III, 
Figs.  I  and  3.)  These  reactions  may  be  made  quantitative  by 
using  neutral,  fairly  concentrated  solutions  and  adding  an  equal 
volume  of  alcohol. 

Both  of  these  double  salts  are  soluble  in  excess  of  alkali,  and 
reprecipitated  by  HCl. 

Stannous  chlorid  reduces  PtCU  to  PtCU  but  forms  no  pre- 
cipitate. Metalhc  Zn  will  precipitate  platinum  as  a  fine  black 
powder  or  spongy  mass. 

Analysis  of  Group  II. 

Separation  of  parts  (a)  and  (b) . 

A  portion  of  the  clear  filtrate,  from  Group  I,  containing  a 
slight  excess  of  HCl  is  tested  for  metals  of  Group  II  by  the 
addition  of  H2S  water.* 

*  A  preliminary  test  is  made  on  a  part  of  the  solution  because  in  the  absence 
of  Group  II,  the  analysis  of  Group  III  can  be  made  more  easily  without  the  pres- 
ence of  H2S. 


38     SALTS  OF    THE  METALS  AND  QUALITATIVE  ANALYSIS 

If  a  precipitate  is  obtained,  warm  the  whole  of  the  solution 
and  pass  in  H2S  gas  for  from  three  to  five  minutes,  which  pre- 
cipitates all  metals  of  the  group  as  sulphids.     Filter. 

Break  point  of  filter-paper  with  glass  rod  and  wash  Group  II 
into  beaker  with  warm  (NH4)2S;   digest  hot  for  a  few  minutes. 

Filter  and  wash  the  precipitate  till  wash-water  shows  only 
traces  of  CI.     Throw  away  all  wash-water  except  the  first. 


Group  II  (a).  Cu,  Cd,  Bi,  Hg,  and  Pb. 


i^^   Group  II  (b).     As,  Sb,  Sn,  Au,  and  Pt. 


Analysis  of  Group  II     (a). 

Dissolve  the  precipitate  off  the  paper  with  hot  dilute  HNO3. 


Hg,  if  present,  will  remain  on  paper,  black. 


Filtrate  contains  nitrates  of  Pb,  Cu,  Cd,  and  Bi. 


Test  black  residue  on  paper  for  Hg"  by  dissolving  in  aqua 
regia  and  precipitating  with  SnCl2.  For  reaction  between  SnCl2 
and  HgCl2  see  page  24.  Aqua  regia  may  be  made  by  mixing 
two  or  three  parts  of  HCl  with  one  part  of  HNO3.  Free  CI  is 
liberated  which  dissolves  the  HgS  as  HgCl2. 

3  HCl  +  HNO3  =  NOCl  +  2  H2O  -+-  CI2. 

If  lead  is  present  in  Group  I,  the  filtrate  above  will  con- 
tain traces  which  must  be  separated  by  adding  a  few  drops  of 
H2SO4  and  allowing  to  staqi^  at  least  fifteen  minutes.     Filter. 


METALS  OF  GROUP  II. 


39 


PbS04  remains  on  paper. 
Filtrate  contains  Cu,  Cd,  Bi. 

To  the  filtrate  add  NH4OH  till  alka- 
line; Bi  separates  as  Bi(0H)3,  white.     Filter. 


Bi(0H)3. 


Cu  and  Cd. 


Divide  the  filtrate  (Cu  and  Cd)  into  two  parts.  A  blue  color 
indicates  presence  of  Cu.  With  one  part  test  for  Cu  by  making 
it  acid  with  acetic  acid  and  adding  K4FeCy6,  which  will  give 
a  brown  precipitate  of  Cu2FeCy6.  With  the  other  part  test 
for  Cd  by  adding  solid  KCN  very  carefully  till  all  blue  color 
has  disappeared;  then  a  Httle  H2S  water  will  give  a  yellow  pre- 
cipitate of  CdS  if  cadmium  is  present. 

Analysis  of  Group  II    (h). 

To  the  ammonium  sulphid  add  HCl  till  acid.  A  very  fine 
white  precipitate  may  be  sulphur  only. 

Filter  and  wash.  Throw  away  wash-water.  Pierce  filter 
and  wash  sulphids  into  large  test-tube  or  small  beaker.  Add 
10  c.c.  of  (NH4)2C03  and  heat  for  a  few  minutes.     Filter. 


Sb,  Sn,  Au,  Pt  sulphids. 


Arsenic  sulphid. 


40     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Add  HCl  and  Zn  and  make  Gutzeit's  test  (page  28)  and  if 
necessary  Fleitmann's  (page  29)  or  Marsh's  (page  32). 

Dry  this  precipitate  upon  paper  and  place  paper  and  pre- 
cipitate in  a  porcelain  evaporator,  add  concentrated  HCl  and 
heat.  (This  must  be  done  under  the  hood.)  Dilute  and  filter, 
when  Au  and  Pt  will  remain  undissolved. 


Au  and  Pt. 


Sb  and  Sn. 


To  the  Sb  and  Sn  solution  add  a  little  Zn  and  a  piece  of 
platinum-foil.  The  antimony  and  tin  will  both  be  reduced  to 
the  metallic  state,  the  Sb  being  deposited  on  the  Pt  as  a  brown 
or  black  coating.  Presence  of  Sb  may  be  confirmed  by  remov- 
ing the  Pt,  washing  carefully,  treating  with  (NH4)2S,  and  dry- 
ing, when  the  coating  will  become  Sb2S3,  orange-red. 

To  the  solution  to  be  tested  for  Sn  add  HCl  enough  to  dis- 
solve all  the  Zn  which  has  been  added,  filter,  and  test  filtrate  with 
HgCl2(page38). 

Dissolve  the  insoluble  residue  of  Au  and  Pt  (the  residue 
will  be  dark-colored  if  either  of  these  metals  are  present)  in 
aqua  regia  and  divide  solution  into  two  parts. 

Test  one  part  for  gold  with  solution  of  FeS04,  or  a  mixture 
of  SnCl2  and  SnCU  (page  36). 

Test  the  other  part  for  Pt  by  adding  NH4CI,  allow  to  stand 
overnight  adding  a  little  alcohol,  and  precipitate  of  ammonium 
platinic  chlorid  will  be  obtained,  yellow  and  crystalHne  (see 
Plate  3,  Fig.  i). 


METALS  OF  GROUP  II.  4 1 

QUESTIONS  ON  GROUP  II. 

Why  is  it  necessary  to  wash  the  precipitate  of  Group  II 
practically  free  from  CI  before  dissolving  in  warm  HNO3  ? 

How  does  the  Hg  found  in  Group  II  differ  from  the  Hg  in 
Group  I? 

How  does  the  Pb  found  in  Group  II  differ  from  the  Pb  in 
Group  I? 

Before  making  the  final  test  for  Sn,  why  is  it  necessary  to 
dissolve  all  the  Zn  which  has  been  added  ? 

In  precipitating  Group  II  why  should  the  solution  be  made 
acid  with  HCl  before  adding  H2S  ? 

Why  is  it  better  to  use  H2S  gas  rather  than  H2S  water  in 
precipitating  metals  of  Group  II  ? 

Before  testing  for  Cd  why  add  KCN  to  decolorize  the  copper 
solution  ? 

Laboratory  Exercise  IV. 
Analytical  reactions  of  the  copper  group  {pages  22-26). 

Laboratory  Exercise  V. 
Analysis  of  copper  and  the  silver  groups. 

Laboratory  Exercise  VI. 
Special  tests  for  arsenic  {pages  28- ji) . 

Laboratory  Exercise  VII. 
Preliminary  reactions  of  the  arsenic  group  {pages  32-^4)  and 
analysis  of  unknown  solutions. 

Laboratory  Exercise  VIII. 
Unknown  solutions. 


42     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Laboratory  Exercises  IX. 
Experiments  with  metals  of  Groups  I  and  II. 

Exp.  lo.  Precipitate  a  little  silver  chlorid  according  to  the 
following : 

AgNOs  +  NaCl  =  AgCl  +  NaNOs. 

Filter  and  allow  the  precipitate  to  become  nearly  dry.  Mix  a 
little  of  the  precipitate  with  powdered  charcoal,  and  heat  be- 
fore the  blowpipe  until  a  globule  of  metallic  silver  is  obtained. 

Exp.  II.  Mix  intimately  a  small  quantity  of  litharge  and 
powdered  charcoal.  Heat  in  a  blowpipe  flame  and  obtain  a 
particle  of  metallic  lead. 

Exp.  12.  In  a  solution  of  lead  (acetate  or  nitrate)  suspend 
a  strip  of  zinc.  Set  aside  for  several  hours  and  note  the  sepa- 
ration of  metallic  lead.     Write  the  reaction. 

Exp.  13.  Put  a  small  quantity  of  cinnabar  (HgS)  into  a 
small,  hard  glass  tube  open  at  both  ends.  Hold  the  tube,  slightly 
inclined,  in  a  strong  heat  of  the  Bunsen  flame;  then  examine  the 
sublimate  under  the  microscope.     What  becomes  of  the  sulphur? 

Exp.  14.  Hold  a  strip  of  iron  or  steel  (knife  blade)  for  a 
few  seconds  in  a  solution  of  copper  sulphate.  Does  the  strip  of 
iron  dissolve  ?     If  so,  in  what  combination  ? 

Exp.  15.  In  an  open,  hard  glass  tube,  heat  strongly  a  mix- 
ture of  charcoal  and  copper  oxid.     Explain  the  change  of  color. 

Exp.  16.  To  a  very  small  piece  of  copper  foil  in  a  test-tube, 
add  a  little  ammonium  chlorid  solution  and  allow  to  stand. 


CHAPTER   V. 
METALS   OF   GROUP  III. 

Iron,     Fe  (Ferrum).     - 

The  Metal. — Atomic  weight  55.9. 

Melting-point  1275°  C.  Iron  occurs  widely  distributed  in 
nature  combined  with  oxygen  as  Fe203  or  Fe304,  with  sulphur 
as  FeSa,  and  with  carbon  as  FeCOa. 

The  reduction  of  iron  from  its  ores  is  typical  of  one  of  the 
four  general  methods,  that  is,  reduction  by  carbon.  This  is 
carried  out  in  the  blast  furnaces,  which  are  so  constructed  that 
a  supply  of  coal,  iron  ore,  and  fusible  slag,  introduced  at  the 
top  of  the  furnace,  are  dissolved  and  hold  impurities,  while  the 
purified  molten  metal  is  withdrawn  from  the  bottom.  This 
melted  iron,  cast  in  molds  as  it  comes  from  the  furnace,  con- 
stitutes our  cast  iron,  is  brittle,  and  contains  a  considerable 
proportion  of  carbon  and  other  impurities. 

Wrought  iron  is  produced  by  working  melted  iron  in  specially 
constructed  furnaces  so  that  the  greater  part  of  the  impurities 
are  removed.  By  the  addition,  to  very  pure  iron  after  such 
treatment,  of  carbon,  manganese,  etc.,  steel  is  produced. 

Reduced  iron  or  "iron  by  hydrogen"  is  prepared  by  the  re- 
duction of  the  heated  oxid  or  hydroxid  in  a  stream  of  hydrogen 
gas. 

Compounds.  —  Iron  forms  two  classes  of  salts,  ferrous, 
represented  by  ferrous  sulphate,  FeS04;  and  ferric,  represented 
by  ferric  sulphate,  Fe2(S04)3,  or  ferric  chlorid,  FeCls. 

Ferric  sulphate,  also  known  as  Monsel's  salt,  is  used  as  a 
st3rptic. 

43 


44     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Ferric  chlorid,  FeCls  or  Fe^Cle,  is  made  by  dissolving  iron 
in  hydrochloric  acid,  oxidizing  the  ferrous  chlorid  with  nitric 
acid,  and  then  driving  ojBf  the  nitric  acid  by  evaporation.  The 
resulting  solution,  however,  contains  traces  of  free  nitric  and 
considerable  free  hydrochloric  acid.  In  the  tincture  of  chlorid 
of  iron  these  acids  react  with  the  alcohol  forming  various  ethers, 
to  which  the  peculiarities  of  the  tincture  may  be  due. 

Copperas  and  green  vitriol  are  commercial  names  for  crys- 
tallized ferrous  sulphate.  FeS047H20  is  used  as  a  disinfectant 
and,  to  a  slight  extent,  in  medicine  as  an  astringent. 

Ferrous  carbonate,  (FeC03)x(Fe(OH)2)3',  prepared  by  double 
decomposition  between  FeS04  and  potassium  or  sodium  car- 
bonate, is  a  medicinal  preparation  quite  largely  used  as  "Blaud's 
pills." 

Analytical  Reactions.  —  A  solution  for  demonstrating  the 
reactions  of  ferrous  salts  is  best  made  by  saturating  cold  dilute 
sulphuric  acid  with  clean  iron  wire.  A  3  to  5  per  cent  solution 
of  fresh  crystals  of  ferrous  ammonium  sulphate  may  be  used. 
The  ordinary  ferrous  sulphate  or  "copperas"  is  almost  sure  to 
contain  some  ferric  salt.  Use  a  2  to  3  per  cent  solution  of  ferric 
chlorid  and  make  the  following  tests,  comparing  the  deport- 
ment of  the  ferrous  and  ferric  solutions  with  each  reagent. 
Write  the  reactions. 

H2S  with  pure  ferrous  salts  gives  no  reaction;  with  ferric 
salts  the  iron  is  reduced  to  the  ferrous  combination,  but  gives 
no  precipitate  except  sulphur. 

(NH4)2S  gives  with  ferrous  iron  a  black  precipitate  of  FeS; 
with  ferric  salts  it  gives  a  precipitate  containing  FeS  and  S. 

NH4OH  precipitates  Fe"  as  ferrous  hydroxid,  Fe(0H)2; 
white  if  perfectly  pure,  but  usually  a  dirty  green  from  admix- 
ture of  ferric  compounds.  The  presence  of  NH4CI  prevents 
a  complete  precipitation  as  Fe(0H)2. 

With  ferric  salts,  NH4OH  completely  precipitates  the  iron 
as  brick-red  ferric  hydroxid,  Fe(0H)3. 


METALS  OF   GROUP  III.  45 

K4FeCy6  gives  with  ferrous  salts  a  bluish-white  precipitate 
of  potassium  ferrous  ferrocyanid,  K2FeFeCy6. 

With  a  solution  of  ferric  salts  the  deep  Prussian  blue,  ferric 
ferrocyanid,  Fe4(FeCy6)3,  is  thrown  out. 

With  potassium  ferricyanid,  ferrous  salts  give  a  dark-blue 
precipitate  of  ferrous  ferricyanid,  Fe3(FeCy6)2-  With  ferric 
salts  no  precipitation  occurs,  but  the  color  may  change  to  green 
or  brown. 

KCyS  or  NH4CyS  gives  no  reaction  with  pure  ferrous  salts, 
but  with  ferric  salts  a  deep  red  solution  of  ferric  thiocyanate, 
Fe(CyS)3,  is  produced.  This  red  color  is  destroyed  by  addi- 
tion of  HgCl2,  not  affected  by  HCl,  and  may  be  extracted  from 
the  aqueous  solution  by  shaking  with  ether  in  which  the 
Fe  (CyS)3  is  soluble. 

Aluminum,  A1. 

Atomic  weight  27.1.  Melting-point  700°  C.  Aluminum 
as  a  constituent  of  clay,  feldspar,  mica,  etc.,  constitutes  a  con- 
siderable part  of  the  earth's  crust. 

Alloys.  —  Aluminum  alloys  are  not  difficult  to  produce,  but 
few  are  of  practical  value.  The  pure  metal  is  used  in  making 
plates.     The  following  may  be  noted. 

Aluminum  alloys  for  bridge  work.  Dr.  Richards,  Paris, 
Dental  Cosmos,  March,  1912,  page  378, 

«  (i)  (2) 

Copper 5.5  Tin 7 

Tin 2.0  Zinc 10 

Aluminum 92.5  Aluminum 83 

Number  two  is  more  elastic  than  number  one  and  either 
makes  a  better  appearance  than  pure  aluminum. 

Compounds.  —  The  most  important  soluble  salts  of  Al  are 
ammonia  alum,  NH4AI (804)2  12  H2O,  potash  alum,  KAl (804)2 
12  H2O,  and  aluminum  sulphate,  AI2 (804)3. 

The  term  alum  is  apphed  to  any  salt  of  definite  crystalline 


46     SALTS  OF   THE  METALS   AND  QUALITATIVE  ANALYSIS 

form  containing  one  molecule  of  a  univalent  sulphate,  such  as 
K2SO4  or  Na2S04,  combined  with  one  molecule  of  a  trivalent 
sulphate,  Al2(S04)3,  Fe2(S04)3  or  Cr2(S04)3,  and  crystallized  with 
twenty-four  molecules  of  water.  The  formula  of  alum,  as  given 
above,  comprises  just  one  half  of  this  combination.  Alum  need 
not  contain  any  aluminium  whatever  so  long  as  it  conforms  to  the 
foregoing  requirements,  e.g.,  chrome  alum  may  be  NH4Cr (804)2 
12  H2O  and  ferric  alum  is  usually  NH4Fe(S04)2  12  H2O. 

Analytical  Reactions.  —  Use  a  5%  solution  of  either  of  these 
for  the  following  tests : 

AI2  (504)3  with  (NH4)2S  and  H2O  gives  a  white  precipitate 
of  A1(0H)3.     Write  the  reaction. 

A1(0H)3  is  likewise  produced  by  NH4OH,  NasCOg,  or  NaOH; 
the  precipitate  is  soluble  in  excess  of  fixed  alkali  hydroxids  with 
formation  of  aluminates: 

A1(0H)3  +  KOH  =  KAIO2  +  2  H2O. 

The  alkaline  aluminates  may  also  be  formed  by  fusion  with 
Na2C03  and  KNO3  and  then  may  be  dissolved  in  hot  water. 

From  the  solution  of  KAIO2  the  Al  may  be  precipitated  as 
Al(OH)3  by  excess  of  NH4CI  (difference  from  Zn,  page  55). 

The  presence  of  organic  acids,  tartaric,  oxalic,  etc.,  inter- 
feres with  the  precipitation  of  aluminium  hydroxid  and  may 
entirely  prevent  it.     The  presence  of  ammonium  chlorid  favors 

its  precipitation. 

Chromium,  Cr. 

Atomic  weight  52.1.  Occurs  as  chrome  iron  ore  or  chromite, 
FeOCr203.  Chromium  forms  two  oxids,  one  basic  in  character, 
Cr203,  which  forms  the  basis  of  chromic  salts,  as  Cr2 (804)3, 
Cr2Cl6(CrCl3),*  etc.;  the  other,  CrOs,  is  an  acid  anhydrid, 
crystallizes  as  dark-red  needles,  and  gives  rise  to  two  series  of 
salts:  neutral  chromates,  such  as  K2Cr04,  and  acid  chromates 
or  dichromates,  K2Cr207. 

*  There  is  a  series  of  chromous  salts,  CrCl2,  Cr(0H)2,  etc.,  corresponding  to 
a  chromous  oxid,  CrO,  but  the  oxid  itself  is  not  known 


METALS  OF  GROUP  III.  47 

The  soluble  chromic  salts  most  easily  obtained  are  chrome 
alum,  KCr (504)2,  chromic  sulphate,  Cr2 (804)3,  and  chromic 
chlorid,  CrClg.  With  a  5%  solution  of  either  of  these  the  fol- 
lowing may  be  demonstrated: 

Cr2(SO)3  with  (NH4)2S  gives  greenish  precipitate  of  Cr(0H)3. 

Similarly  to  Al,  the  chromium  hydroxid  is  precipitated  by 
the  alkaline  carbonates  and  the  alkaline  sulphids  as  well  as  by 
the  hydroxids;  and  then  by  boihng  the  Cr(0H)3  with  NaOH 
or  KOH,  or  by  fusing  with  Na2C03  and  KNO3,  chromates  of  the 
alkalis  are  produced. 

The  sohd  dichromate  K2Cr207  with  strong  H2SO4  gives,  in 
the  presence  of  chlorids,  the  reddish-brown  gas  Cr02C]2  (chloro- 
chromic  anhydrid  or  chromium  dioxychlorid)  used  as  a  test 
for  chlorids  (page  90) . 

Analysis  of  Group  III. 

(Fe,  Al,  Cr.     Phosphates  and  oxalates  being  absent.) 

The  filtrate  from  Group  II  must  be  freed  from  H2S  by  boil- 
ing with  a  few  drops  of  HNO3  in  a  porcelain  dish  till  a  drop 
removed  by  a  glass  rod  does  not  blacken  filter-paper  wet  with  a 
solution  of  lead  acetate.  This  treatment  also  serves  to  oxidize 
the  iron  (reduced  by  H^S)  to  ferric  salt  and  at  the  same  time 
concentrates  the  solution.  To  the  clear  solution  thus  obtained 
add  10  c.c.  of  NH4CI  solution,  then  NH4OH  till  alkaline,  when 
the  metals  of  this  group  will  separate  out  as  hydroxids:  Fe(0H)3 
brick-red,  A1(0H)3  white,  Cr(0H)3  bluish-green.  Filter,  Wash 
carefully,  and  dry  precipitates,  removing  paper  from  funnel. 


Group  III. 


Groups  IV,  V,  and  VI. 


48     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 


Scrape  dried  precipitate  from  paper  in 
a  crucible  and  cover  well  with  a  mixture  of 
dry  Na2C03  and  KNO3  and  fuse,  keeping 
fusion  liquid  for  at  least  three  minutes. 
Cool.  Boil  the  fused  mass  with  H2O. 
Filter. 


Al  and  Cr. 


Iron  will  remain  on  the  paper;  Al  and  Cr  will  be  in  solution 
as  alkaline  aluminate  and  chromate. 

Divide  filtrate  (Al  and  Cr)  into  two  parts.  Test  one  por- 
tion for  Al,  by  acidifying  with  HCl,  adding  (NH4)2C03  till 
alkaline,  and  boiling,  when  Al  will  separate  as  a  white  floccu- 
lent  precipitate  of  Al2(OH)6. 

Test  second  portion  of  filtrate  for  Cr  by  acidifying  strongly 
with  acetic  acid,  boiling  to  expel  CO2,  and  adding  a  few  drops  of 
a  solution  of  lead  acetate.  A  yellow  precipitate  (PbCr04)  in- 
dicates Cr. 

Wash  the  precipitate  remaining  on  the  paper  (Fe)  and  dis- 
solve in  dilute  HCl.  Divide  resulting  solution  (FeCls)  into 
two  parts  and  confirm  presence  of  Fe  by  testing  one  with  K4FeCy6 
(blue  precipitate)  and  the  other  with  KCyS  (red  solution) . 

If  iron  is  found,  determine  in  original  substance  whether 
ferrous  or  ferric,  by  use  of  tests  described  on  pages  44  and  45. 

QUESTIONS  ON  GROUP  III. 
Why  boil  off  H2S  before  precipitating  the  group  with  NII4OH  ? 
Why  addHNOg? 


METALS   OF   GROUP   III.  49 

Of  what  use  is  the  nitrate  of  potash  (KNO3)  in  the  fusion 
of  the  hydroxids  of  Al  and  Cr? 

In  making  the  final  test  for  Cr  why  is  it  necessary  to  add 
acetic  acid,  and  why  boil  off  the  CO2  ? 

Why  must  HCl  be  added  before  making  the  final  test  for 
Alwith  (NHOaCOs? 

Laboratory  Exercise  X. 

Iron,  Aluminum,  and  Chromium. 

Exp.  17.  (a)  To  5  c.c.  of  dilute  alum  solution  containing  a 
little  NH4CI,  add  NH4OH  solution  and  heat. 

Note.  —  NH4CI  aids  in  the  complete  separation  of  the  Al2(OH)6. 

Write  reaction.  Will  the  precipitate  dissolve  in  an  excess  of 
the  reagent  ? 

{h)  Repeat,  using  a  chromium  solution  in  place  of  the  alum. 
Exp.  18.  Dissolve  a  few  crystals  of  FeS04  in  water.  Filter, 
if  necessary,  and  to  a  portion  of  the  clear  solution  add  a  little 
ammonia  water.  To  another  portion  add  a  few  drops  of  HNO3 
and  boil  for  two  or  three  minutes.  Carefully  add  ammonia 
water  till  a  permanent  precipitate  is  obtained. 

To  a  solution  of  ferric  alum  add  a  little  ammonia.  What 
change  is  produced  by  the  HNO3  in  the  second  part  of  the 
experiment. 

FeS04  +  NH4OH  =  ? 
3  H2SO4  +  6  FeS04  +  2  HNO3  =  ? 
Fe2(S04)3  +  NH4OH  =  ? 

Note.  —  The  addition  of  sulphuric  acid  is  not  necessary  to  the  oxidation  by 
HNO3.     It  simplifies  the  reaction,  as  otherwise  more  or  less  ferric  nitrate  is  formed. 

Exp.  ig.  Make  a  little  fresh  solution  of  potassium  ferricy- 
anide,  also  a  solution  of  ferrous  sulphate,  to  which  add  a  little 
H2SO4  and  a  piece  of  iron  wire.     After  hydrogen  ceases  to  be 


50     SALTS  OF  THE  METALS  AND  QUALITATIVE  ANALYSIS 

evolved  make  the  following  tests,  completing  the  reaction  in 
each  case: 

FeS04  +  KsFeCye  =  ?  FcsCle  +  KgFeCye  =  ? 

FeS04  +  K4FeCy6  =  ?  FezCle  +  K4FeCy6  =  ? 

FeS04  +  KCyS  =  ?  FeaCle  +  KCyS  =  ? 

Exp.  20.  To  a  solution  of  chrome  alum  add  a  Httle  NH4OH. 
Filter,  wash  the  precipitate  once  or  twice  and  allow  to  dry. 

Cr2(S04)3  +  NH4OH  =  ? 

Exp.  21.  To  the  dried  precipitate  obtained  in  Exp.  20  add 
a  little  dry  sodium  carbonate  and  potassium  nitrate.  Mix: 
thoroughly,  transfer  to  a  porcelain  crucible  and  heat  strongly 
for  several  minutes,  cool  and  note  the  color  of  the  fused  mass. 
Dissolve  in  water,  acidify  with  acetic  acid,  and  divide  the  solu- 
tion into  two  parts;  to  the  first  add  a  few  drops  of  a  solution 
of  Pb(N03)2  or  Pb(C2H302)2,  and  to  the  second  a  few  drops  of 
BaCl2. 

Exp.  22.  To  separate  solutions  of  aluminum,  iron,  and 
chromium  salts,  add  (NH4)2S.  Iron  alone  forms  a  sulphid;  the 
other  two  give  precipitates  of  hydroxids.     Write  the  reactions. 

Laboratory  Exercises  XI  and  XII. 

Analyses  of  unknown  solutions  containing  metals  of  Groups  /,, 
11,  and  III. 


CHAPTER  VI. 
METALS   OF   GROUP  IV. 

Cobalt,  Co. 

The  Metal.  —  Atomic  weight  59.0.  Cobalt  occurs  in  nature 
as  an  arsenide  C0AS2,  smaltite;  also  CoAsS,  cobaltite.  These 
ores  are  poisonous  and  have  in  times  past  caused  the  miners  so 
much  trouble  that  the  name  cobalt  was  applied  to  them,  the 
word  meaning,  "A  demon  or  mountain  sprite. "  MetalHc  arsenic 
has  also  been  called  cobalt.  These  facts  are  probably  responsi- 
ble for  a  reputation  which  is  attached  to  the  pure  oxid  of  cobalt. 

Analytical  Reactions. — Use  a  2%  solution  of  nitrate. 
CrystalHne  salts  of  Co  are  usually  of  pink  color;  anhydrous 
salts  are  blue. 

Co(N03)2  with  (NH4)2S  gives  precipitate  of  CoS,  black.  Test 
solubility  of  this  precipitate  in  HCl. 

Make  a  borax  bead  by  fusing  a  Uttle  borax  on  the  looped  end 
of  a  clean  platinum  wire.  When  a  bead  of  clear  "borax  glass" 
has  been  obtained,  dip  it  in  a  little  of  the  CoS  just  formed,  and 
fuse  again.     The  color  of  the  bead  when  cold  is  a  deep  blue. 

Note. — Be  sure  and  make  the  fusion  complete;  the  use  of  an  insufScient 
amount  of  heat  will  account  for  much  of  the  trouble  experienced  by  students  in 
obtaining  satisfactory  bead  tests. 

Co(N03)2  with  KNO2  forms  a  double  nitrite,  Co(N02)2 
2  KNO2,  soluble  in  water;  but  if  sufficient  acetic  acid  is  added 
to  produce  a  strong  acid  reaction,  the  solution  heated,  and  then 
allowed  to  stand  overnight,  the  cobalt  is  completely  precipitated 
as  another  double  salt,  Co(N02)3,3KN02,  yellow  and  crystalline. 

SI 


52     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Nickel,  Ni. 

Atomic  weight  58.7.  Occurs  associated  with  Co,  some- 
times with  Fe  as  sulphid. 

The  metal  is  white,  hard,  and  has  a  high  melting-point.  It 
is  soluble  in  dilute  mineral  acids,  most  easily  in  nitric.  It  is 
the  least  malleable  of  the  common  metals. 

Alloys.  —  The  principal  alloys  are  German  silver,  containing 
copper,  nickel,  and  zinc,  and  an  alloy  of  25%  nickel  and  75% 
copper,  used  by  the  United  States  Government  in  making  five- 
cent  pieces. 

Nickel  is  largely  used  for  plating  steel  and  copper. 

Analytical  Reactions.  —  Use  a  2%  solution  of  the  sulphate 
or  nitrate.  NiS04  with  (NH4)2S  gives  NiS,  black.  Test  solu- 
bihty  in  HCl. 

The  borax-bead  test  applied  to  NiS  or  other  nickel  salt  gives 
a  bead  yellowish  brown  when  cold,  but  the  color  is  easily  masked 
by  other  metals. 

Ni  salts  with  KNO2  give  the  soluble  double  nitrite  of  similar 
composition  to  the  Co  salt,  Ni(N02)2,  2  KNO2.  The  nickel 
salt,  unHke  the  cobalt,  is  not  easily  decomposed,  and  is  not 
precipitated  by  heating  with  acetic  acid.  Advantage  is  taken 
of  this  fact  in  effecting  the  separation  of  cobalt  from  nickel 
(page  56). 

Manganese,  Mn. 

Atomic  weight  55.0.  Occurs  chiefly  as  the  dioxid,  Mn02, 
pyrolusite. 

Compounds.  —  The  black  oxid,  Mn02,  is  commercially  im- 
portant in  the  production  of  chlorin.  By  Weldon's  process, 
the  chlorin  is  obtained  from  HCl,  the  pyrolusite  acting  as  an 
oxidizing  agent. 

The  oxidization  of  MnOa  in  the  presence  of  KOH  results  in 
the  formation  of  potassium  permanganate,  KMn04.  This  salt 
is  a  valuable  disinfectant  and  is  largely  used.     Its  decomposition 


METALS  OF   GROUP  IV.  53 

furnishes  5  atoms  of  available  oxygen  from  every  double  mole- 
cule (KzMnaOs). 

Condy's  fluid,  a  commercial  disinfectant,  is  a  solution  of 
KMn04. 

Manganese  salts  are  usually  flesh-colored. 

Analytical  Reactions.  —  A  3%  solution  of  the  sulphate  may 
be  used  in  the  following  tests: 

MnS04  with  (NH4)2S  gives  flesh-colored  precipitate  of  MnS. 
Test  solubihty  in  HCl.  With  a  httle  of  the  precipitated  MnS 
make  a  red-lead  test  for  Mn  as  follows : 

Place  in  a  test-tube  a  little  red  lead  (Pb304).  Add  three  or 
four  cubic  centimeters  of  a  solution  of  nitric  acid  (about  one 
part  of  concentrated  HNO3  and  one  of  H2O) ,  and  boil  well.  Add, 
by  means  of  a  glass  rod,  a  httle  of  the  washed  MnS  to  the  mix- 
ture in  the  tube  and  boil  again.  Now  dilute  with  water  till  the 
tube  is  about  three-quarters  full,  and  allow  to  stand  till  hquid 
is  clear.  If  Mn  is  present,  the  supernatant  fluid  will  be  a  pink 
to  red  color  due  to  the  formation  of  permanganic  acid, 
HMn04. 

Note.  —  HCl  or  chlorids,  even  in  small  quantities,  interfere  with  the  reaction; 
hence  it  is  recommended  to  make  the  test  on  the  sulphid.  Reducing  agents  must 
likewise  be  absent.  When  these  precautions  are  observed  the  test  is  a  very  simple 
and  an  extremely  delicate  one. 

MnS04  with  NaOH  gives  flesh-colored  Mn(0H)2  insoluble 
in  excess  of  reagent  (separation  from  Zn). 

Upon  fusion  with  a  mixture  of  KNO3  and  Na2C03,  man- 
ganese salts  produce  green  manganates,  as  Na2Mn04. 

Zinc,  Zn. 

The  Metal.  —  Atomic  weight  65.4.  Melting-point  420°  C. 
(burns).  Occurs  chiefly  as  the  carbonate,  ZnCOs,  calamine.  A 
native  carbonate  of  zinc  is  also  known  as  smithsonite.  The 
sulphid,  ZnS  (zinc  blende),  and  the  silicate  are  also  natural  sources 
of  the  metal. 


54     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

These  ores  of  zinc,  whether  sulphate  or  carbonate,  upon 
roasting  in  air  are  converted  into  oxide,  and  the  oxide  is  easily 
reduced  by  carbon  to  metallic  zinc.  The  metal  is  bluish  white 
in  color,  melts  at  420°  C;  is  brittle  at  ordinary  temperatures, 
but  malleable  and  ductile  at  140°  to  150°  C.  At  200°  C,  how- 
ever, it  again  becomes  brittle  and  fuses  as  above  stated  at  420°  C. 
At  950°  zinc  boils  and  may  be  distilled;  in  air  it  ultimately 
burns  to  a  white  sulphate. 

Alloy.  —  Zinc  is  of  considerable  importance  from  a  dental 
standpoint,  the  metal  itself  being  used  in  the  manufacture  of 
counter- dies  and  solders;  and,  according  to  Mitchells'  Dental 
Chemistry,  it  may  be  advantageously  used  in  the  proportion  of 
I  to  1.5%  in  silver-tin  amalgam  alloys.  "  It  tends  to  control 
shrinkage,  imparts  a  'buttery'  plasticity  to  the  amalgam,  adds 
to  the  whiteness  of  the  filling  and  assists  in  the  maintaining  of  its 
color." 

Compounds.  —  The  oxide  of  zinc  combines  with  phosphoric 
acid  and  is  peculiarly  adapted  to  the  preparation  of  dental 
cements.  Zinc  salts  with  alkaline  carbonates  precipitate  a 
white  basic  carbonate,  Zns (OH) 6(003)2,  which  is  used  as  a  pig- 
ment in  the  preparation  of  paint  and  also  as  a  source  of  pure 
oxide  of  zinc. 

The  sulphate,  ZnS04,  also  known  as  white  vitriol,  is  per- 
haps the  most  common  salt.  The  chlorid  is  a  constituent 
of  many  commercial  Hquid  disinfectants  and  antiseptics.  The 
nitrate  also  is  easily  obtained. 

A  2  or  3  per  cent  solution  of  any  of  these  soluble  salts  may  be 
used  in  the  following  tests : 

Analytical  Reactions.  —  ZnS04  with  (NH4)2S  gives  a  white 
precipitate  of  ZnS. 

Sulphid  of  zinc  is  the  only  white  sulphid  formed  in  the  course 
of  analysis  of  ordinary  solutions,  but  the  following  white  pre- 
cipitates are  formed:  Sulphid  of  manganese  is  flesh-colored  or 
dirty  white.     Aluminum  hydroxid  resembles  sulphid  of  zinc  in 


METALS  OF   GROUP   IV.  55 

appearance  and  is  precipitated  by  (NH4)2S.  Yellow  (NH4)2S 
added  to  an  acid  solution  will  precipitate  sulphur,  white,  very 
fine  and  difficult  to  filter  out. 

ZnS04  with  NaOH  (or  KOH)  gives  a  white  gelatinous  pre- 
cipitate of  zinc  hydrate,  Zn(0H)2,  soluble  in  excess  of  the  reagent 
as  Na2Zn02  (sodium  zincate). 

Note.  —  Colorless  gelatinous  precipitates  in  slight  amounts  may  escape  de- 
tection, as  it  sometimes  takes  careful  observation  to  see  them,  especially  if  the 
laboratory  light  happens  to  be  poor. 

Na2Zn02  with  H2S  or  (NH4)2S  gives  precipitate  of  ZnS. 

From  solution  of  Na2Zn02  the  Zn  may  be  precipitated  as 
Zn(0H)2  by  addition  of  NH4CI,  but  further  addition  of  the 
NH4CI  redissolves  the  precipitate  (distinction  from  Al,  page  46). 

ZnS04  with  K4FeCy6  gives  white  precipitate  of  zinc  ferro- 
cyanid  (Zn2FeCy6) ,  insoluble  in  NH4OH. 

Note.  — ■  The  ferrocyanid  and  the  sulphid  are  the  only  two  zinc  salts  not  soluble 
in  NH4OH.     (Prescott  and  Johnson,  page  179.) 

Soluble  zinc  salts,  with  oxalic  acid  or  oxalates,  give  a  pre- 
cipitate of  zinc  oxalate  sufficiently  insoluble  in  alcohol  and 
water  to  make  it  available  for  use  in  the  quantitative  separation 
of  zinc  from  dental  alloys.  The  crystals  are  of  characteristic 
form,  which  may  be  recognized  under  a  microscope  (Plate  II, 
Fig.  6,  page  162). 

Analysis  of  Group  IV. 

(Co,  Ni,  Mn,  Zn.) 

(In  the  presence  of  phosphates,  oxalates,  borates,  etc., 
examine  this  group  by  the  scheme  given  on  page  80). 

To  the  clear  filtrate  from  Group  III  add  (NH4)2S.  A  pre- 
cipitate may  be  NiS,  CoS,  MnS,  and  ZnS.  Wash  the  precipitate 
and  treat  with  cold  dilute  HCl,  which  will  dissolve  MnS  and  ZnS 
only. 


56     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 


CoS  and  NiS,  black. 


MnCl2  and  ZnCU  in  solution. 


Make  a  borax-bead  test  (page  51)  of  the  precipitates.  If 
a  clear  red-brown  bead  is  obtained,  Ni  alone  is  present.  If 
the  bead  is  blue,  Co  is  present,  Ni  may  or  may  not  be. 

Separation  of  Cobalt  and  Nickel. 

If  Co  is  present,  dissolve  the  black  precipitate  off  the  paper 
with  aqua  regia,  evaporate  in  porcelain  capsule  practically  to 
dryness,  dissolve  in  H2O,  add  excess  of  acetic  acid  and  potassium 
nitrite  (KNO2).  Allow  to  stand  over  night,  when  Co  will 
separate  out  as  a  yellow  crystalline  precipitate  (page  51). 

Filter  and  test  filtrate  for  Ni  with  NaOH,  which  gives  a 
pale-green  precipitate  of  Ni(0H)2  insoluble  in  excess  of  the 
precipitant. 

Separation  of  Manganese  and  Zinc. 

Boil  the  HCl  solution  of  Zn  and  Mn  to  expel  the  H2S,  then 
add  a  decided  excess  of  KOH  or  NaOH  and  allow  to  stand  ten 
minutes  without  heating.  Mn  will  separate  out  as  Mn(0H)2, 
while  Zn  will  remain  in  solution  as  K2Zn02. 


Mn(0H)2. 


K2Zn02. 


METALS  OF  GROUP  IV.  57 

Test  precipitate  by  the  red-lead  test  for  Mn,  page  53.  Test 
filtrate  for  Zn  by  adding  H2S  or  a  few  drops  of  (NH4)2S,  which 
will  precipitate  ZnS,  white. 

QUESTIONS  ON  GROUP  IV. 

Why  dissolve  the  MnS  and  ZnS  in  cold  and  dilute  HCl  ? 

Why  is  it  necessary  to  separate  all  the  Mn  before  testing 
for  Zn  ? 

If  traces  of  Co  or  Ni  are  dissolved  by  the  HCl,  how  does  it 
affect  the  final  test  for  Zn  ? 

In  this  analysis  (in  absence  of  phosphates,  etc.)  what  im- 
portant difference  between  the  behavior  of  salts  of  Zn  and  Al  ? 

Why  is  it  necessary  to  allow  time  for  complete  precipitation 
of  CowithKNOs? 

Why  expel  H2S  before  separating  Mn? 

Where  does  this  H2S  come  from? 

Laboratory  Exercise  XIIL 
Cobalt,  Manganese,  Nickel  and  Zinc. 

Exp.  23.  Add  to  solutions  of  Co(N03)2,  MnS04,  Ni(N03)2 
and  ZnS04  a  few  drops  of  (NH4)2S  solution. 

Note  color  of  precipitate  and  write  reaction  in  each  case. 

Exp.  24.  On  four  separate  filter  papers  collect  the  several 
precipitates  formed  in  Exp.  23.  Wash  once  with  H2O  and  make 
a  borax-bead  test  with  each  precipitate  as  shown  in  the  labora- 
tory demonstration.  To  each  precipitate  add,  on  the  paper, 
cold  dilute  HCl. 

Exp.  25.  (a)  To  a  solution  of  ZnS04  add  a  Httle  NH4OH. 
Will  the  precipitate  dissolve  in  excess  of  reagent  ? 

(b)  Repeat,  adding  NH4CI  before  using  the  NH4OH. 

(c)  Repeat  (a)  using  NaOH  in  place  of  NH4OH. 

Exp.  26.  Precipitate  a  httle  MnS,  filter  and  wash.  Make 
red-lead  test  as  described  on  page  53. 


58     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Exp.  27.  (a)  To  a  solution  of  Co(N03)2  in  a  test-tube,  add 
a  drop  or  two  of  dilute  NH4OH.  Now  add  an  excess  of  NH4OH 
and  note  if  any  change  occurs. 

(b)  Repeat,  using  a  solution  of  NiS04. 

What  are  the  precipitates  formed  ? 

Exp.  28.  To  a  solution  of  zinc  salt  add  a  solution  of  Na2C03. 
The  precipitate  is  a  basic  carbonate  of  zinc. 

Balance  the  equation 

ZnS04  +  NaaCOa  +  H2O  =  Zn5(OH)6(C03)2  +  Na2S04  +  CO2. 

Exp.  29.  Shake  in  a  test  tube  a  little  ZnO  and  water,  filter 
and  test  filtrate  for  Zn  as  in  Exp.  23. 

Repeat  using  ammonium  chloride  solution  instead  of  the 
water.     Inference. 

LABOIiATORY    EXERCISE    XIV. 

Analytical  reactions  of  metals  of  the  zinc  group.     {Pages  51-56.) 

Laboratory  Exercises  XV  and  XVI. 
Unknown  solutions. 


CHAPTER  VII. 
METALS   OF   GROUP  V. 

The  Alkaline  Earths  Ba,  Sr,  Ca,  Mg. 

The  common  alkaline  earth  metals  present  similarity  of 
properties  which  ally  them  more  closely  than  the  metals  of  some 
of  the  previous  analytical  groups.  None  of  the  metals  occur 
free  in  nature.  The  metals  themselves  are  isolated  with  con- 
siderable difficulty,  with  the  exception  of  magnesium,  and  they 
all  decompose  water  with  evolution  of  hydrogen,  calcium,  stron- 
tium and  barium  producing  the  decomposition  at  ordinary  tem- 
peratures; magnesium,  at  high  temperatures  only. 

As  a  group  they  form  insoluble  carbonates,  from  which  CO2 
is  easily  driven  off  by  heat,  leaving  the  oxid  of  the  metal.  This 
oxid  unites  with  water,  forming  feebly  soluble  hydroxids. 
The  solutions  of  the  hydroxids  are  alkaHne  to  Htmus,  and  are 
used,  to  a  considerable  extent  in  medicine,  as  antacids. 

There  are  two  other  metals  belonging  to  this  group.  The 
first,  glucinum,  also  called  beryUium,  has  an  atomic  weight  of 
9.1.  Soluble  salts  of  glucinum  are  precipitated  by  ammonium 
hydroxid  as  white  and  gelatinous  Be(0H)2.  The  precipitate 
somewhat  resembles  aluminum  hydroxid.  Ammonium  carbon- 
ate also  precipitates  the  hydroxid  which  is  easily  soluble  in  excess 
of  reagent.  The  solution,  however,  should  not  be  boiled  as  pro- 
longed boiling  will  cause  the  glucinum  hydroxid  to  reprecipitate. 

BeryUium  oxid  unites  with  phosphoric  acid,  forming  a  phos- 
phate similar  in  its  properties  to  the  basic  phosphate  of  zinc,  and 
its  use  is  claimed  by  some  manufacturers  to  be  essential  to  the 
preparation  of  artificial  enamels.     (See  page  124.) 

59 


6o     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

The  second  rare  metal  belonging  to  this  group  is  radium; 
atomic  weight  225.  The  metal  itself  has  not  as  yet  been  iso- 
lated. Its  compounds  are  obtained  from  uraninite  or  pitch- 
blende, a  source  of  uranium.  It  is  bivalent,  and  the  chlorids, 
bromids,  nitrates,  and  hydroxids  have  been  studied. 

Radium  compounds  are  luminous,  and  the  active  emanations 
emitted  by  them  have  been  condensed  at  150°  below  zero  centi- 
grade, forming  new  substances,  among  which  helium  has  been 
identified.  The  discovery  of  this  fact  is  responsible  for  our  new 
conception  of  the  possible  divisibihty  or  disintegration  of  what 
were  once  considered  indivisible  atoms,  the  "smoke  ring"  mole- 
cule, and  the  possible  transmutation  of  the  elements. 

Barium,  Ba. 

Compounds.  —  Barium,  the  next  metal  to  radium  in  this 
group  in  point  of  atomic  weight,  which  is  137.4,  occurs  chiefly 
as  a  sulphate  BaS04,  heavy  spar,  and  BaCOs,  witherite.  Barium 
oxid  may  be  formed  by  heating  the  carbonate  or  nitrate  to  red 
heat.  It  absorbs  oxygen  from  the  air  with  formation  of  the 
binoxid  Ba02.  This  in  turn  is  decomposed,  oxygen  being  given 
off  and  BaO  being  reproduced.  The  barium  oxid  hence  be- 
comes a  source  of  oxygen  of  commercial  importance.  The  cost 
of  producing  oxygen  by  this  method  is  obviously  small. 

The  peroxid  of  barium  is  also  of  particular  importance  to  the 
dentist,  in  that  it  is  an  important  source  of  peroxid  of  hydrogen. 
This  substance  is  considered  more  fully  in  a  chapter  on  mouth 
washes  and  local  anaesthetics.     (See  page  171.) 

Barium  hydroxid,  Ba02H2,  slightly  soluble  in  water,  absorbs 
CO2  very  rapidly  and  may  be  used  as  a  test  for  this  gas.  The 
solution  is  known  as  "Baryta  Water." 

Analytical  Reactions.  —  Use  a  2%  solution  of  the  chlorid 
for  tests. 

BaCli  with   (NH4)2C03  gives  white  precipitate  of  barium 


METALS  OF  GROUP    V.         -  6l 

carbonate.     Test  solubility  in  acids.     With  soluble  sulphates 
BaCl2  produces  BaS04  insoluble  in  HCl.     (Test  for  sulphates.) 

BaCl2  with  K2Cr207  or  K2Cr04  gives  yellow  precipitate  of 
BaCr04.  Barium  salts  moistened  with  HCl  and  held  on  a  clean 
platinum  wire  give  to  the  colorless  flame  of  the  Bunsen  burner 
a  green  or  yellowish-green  color. 

Strontium,  Sr. 

Atomic  weight  87.6.  Occurs  as  the  carbonate,  SrCOs, 
strontianite,  also  as  the  sulphate. 

Strontium  salts  are  used  commercially  in  the  preparation  of 
colored  fires,  strontium  imparting  a  vivid  red  color  to  the  flame. 
They  are  not  used  medically.  Strontium  oxalate  crystallizes 
in  practically  the  same  forms  and  much  more  easily  then  cal- 
cium oxalate. 

Analytical  Reactions.  —  Use  a  3  to  4%  solution  of  the  nitrate 
or  chlorid  for  tests. 

Sr(N03)2  with  (NH4)2C03  gives  white  precipitate  of  SrCOs. 

Sr(N03)2  with  H2SO4  or  soluble  sulphate  gives  white  pre- 
cipitate of  SrS04,  rather  more  soluble  in  water  and  more  slowly 
formed  than  BaS04. 

A  saturated  solution  of  SrS04  may  be  used  to  test  for  barium 
in  presence  of  Sr  salts. 

Sr(N03)2  with  K2Cr04  gives  precipitate  of  SrCr04,  but  with 
the  acid  chromate  (dichromate)  of  potassium,  K2Cr207,  no 
precipitate  is  formed  except  in  concentrated  solutions. 

Sr(N03)2  with  oxalic  acid  gives  a  precipitate  of  strontium 
oxalate,  SrC204,  crystallizing  in  the  so-called  envelop  form 
(Plate  II,  Fig.  3,  page  162).  Salts  of  Sr  color  the  Bunsen  flame 
crimson. 

CALcroM,  Ca. 

Atomic  weight  40.1.  Calcium  is  widely  distributed  and 
very  abundant,  limestone,  chalk,  marble,  and  calc-spar  being 


62     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

natural  carbonates;    CaCOs,  gypsum,  and  alabaster  are  sul- 
phates. 

Calcium  phosphate  occurs  in  the  mineral  apatite  and  is  also 
a  principal  constituent  of  animal  bones. 

Calcium  sulphate  is  of  particular  interest,  occurring  as 
gypsum,  CaS04.2  H2O.  Upon  heating,  the  two  molecules  of 
water  of  crystallization  may  be  driven  off,  leaving  the  anhydrous 
CaS04,  or  plaster  of  Paris,  so  largely  used  in  dental  laboratories. 
When  water  is  added  to  the  anhydrous  powder,  it  reunites  in  the 
proportions  of  the  original  crystallized  salt  and  thereby  occasions 
the  "setting"  of  the  plaster.  Essig  states  that  if,  in  the  prep- 
aration of  plaster,  the  heat  is  allowed  to  exceed  127°  C,  its 
affinity  for  water  is  impaired  or  destroyed  and  this  effect  will 
not  be  produced.* 

As  plaster  sets,  more  or  less  expansion  takes  place,  and,  if 
spread  upon  glass,  the  mass  usually  rises  slightly  in  the  center, 
producing  a  plate  which  is  somewhat  concave  on  the  under 
surface.  This  tendency  to  expansion  varies  with  different 
grades  of  plaster,  as  may  easily  be  shown  by  a  method  suggested 
by  Dr.  George  H.  Wilson  in  the  Dental  Cosmos  for  August, 
1905,  page  940,  which  consists  simply  of  filling  small  glass 
beakers  with  mixtures  similarly  prepared.  Some  samples  were 
found  to  expand  so  sHghtly  as  not  to  injure  the  glass,  others 
cracked,  and  some  broke  the  beaker  into  fragments. 

The  method  of  mixing  also  affects  the  amount  of  expan- 
sion. In  a  valuable  article  on  "Experiments  in  Plaster  of  Paris 
to  Test  Expansions,"  by  Dr.  Stewart  J.  Spence,  in  Items  of 
Interest,  1902,  page  721,  it  is  shown  that  "not  only  do  different 
plasters  expand  in  differing  degrees,  but  the  same  plaster  expands 
very  differently  according  to  the  stirring  given  it  before  pouring," 
and  that  long  stirring  increases  the  heat  developed,  the  rapidity 
of  setting,  and  the  amount  of  expansion,  but  decreases  the 
strength. 

*  American  Text-book  of  Prosthetic  Dentistry. 


METALS  OF  GROUP   V.  63 

Various  methods  have  been  prepared  to  overcome  the  diffi- 
culties in  manipulation  of  plaster,  such  as  mixing  the  plaster 
with  alum,  marble-dust,  or  potassium  sulphate.  A  compound 
on  the  market  consists  of  a  mixture  of  plaster  and  Portland 
cement.  A  mixture  which  has  been  very  strongly  recommended 
as  an  investment  preparation  consists  of  two-thirds  plaster  and 
one-third  powdered  pumice-stone. 

Analjrtical  Reactions.  ~  Use  a  3  or  4%  solution  of  CaCl2 
for  tests. 

CaCl2  with  (NH4)2C03  gives  white  precipitate  of  CaCOa, 
easily  soluble  in  acids. 

CaCl2  with  oxalic  acid  or  soluble  oxalates  gives  a  white  pre- 
cipitate of  CaC204,  similar  in  form  to  the  SrC204  but  much  more 
difficult  to  obtain  in  the  crystalline  condition. 

CaS04  is  not  precipitated  except  from  moderately  concen- 
trated solution. 

A  saturated  solution  of  CaS04  may  be  used  to  test  for  stron- 
tium salts  in  presence  of  Ca. 

Magnesium,  Mg. 

Atomic  weight  24.36.  Burns  easily  in  the  air,  forming  MgO. 
Principal  sources  are  the  carbonate,  MgCOs,  magnesite,  and  a 
double  carbonate,  CaMg(C03)2,  dolomite.  The  sulphate  MgS04 
occurs  in  the  mineral  kieserite  in  the  "Stassfurt  deposit." 
"French  chalk"  (or  talcum),  soapstone,  and  meerschaum  con- 
sist of  magnesium  silicate  in  varying  states  of  purity. 

Asbestos  is  a  double  silicate  of  magnesium  and  calcium. 

Compounds.  —  Epsom  salt,  or  magnesium  sulphate,  occurs 
as  a  constituent  of  laxative  waters.  The  crystalhzed  salt, 
MgS04.7  H2O  resembles  oxalic  acid  in  appearance,  and  has  been 
mistaken  in  several  instances  for  the  poisonous  acid. 

Magnesium  carbonate  is  used  in  pharmacy  in  two  forms; 
viz.,  the  Hght  and  the  heavy.     These  are  produced  by  precipi- 


64     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

tating  dilute  or  concentrated  solution  of  magnesium  sulphate 
with  sodium  carbonate. 

The  light  and  heavy  magnesium  oxides  are  produced  by 
calcination  of  the  light  or  heavy  carbonates.  Magnesium  salts 
are  quite  generally  distributed  in  the  human  system,  but  in 
small  quantities.  They  occur  in  the  bones,  the  teeth,  and  the 
various  body  fluids. 

Analytical  Reactions.  —  A  5%  solution  of  the  sulphate  or 
nitrate  may  be  used  in  the  following  tests : 

Magnesium  salts  with  (NH4)2C03  give  a  white  precipitate 
of  basic  carbonate  of  variable  composition.  This  precipitate 
forms  very  slowly  in  dilute  solution,  and  in  the  presence  of 
NH4CI  the  formation  of  soluble  double  salts  prevents  the  pre- 
cipitation altogether. 

MgCl2  with  Na2HP04  gives  in  fairly  concentrated  solution 
a  white  precipitate  of  MgHP04.  In  presence  of  NH4CI  and 
NH4OH  the  alkaline  phosphates  precipitate  magnesium-ammo- 
nium-phosphate, MgNH4P04,6H20,  even  from  very  dilute  solu- 
tion (Plate  IV,  Fig.  2). 

In  case  the  precipitate  has  formed  very  slowly,  it  may  separ- 
ate as  small,  almost  transparent,  crystals  clinging  to  the  sides 
of  the  beaker. 

Ammonium  oxalate  does  not  precipitate  magnesium  solu- 
tions. 

Analysis  of  Group  V. 

(Ba,  Sr,  Ca,  Mg.) 

To  the  filtrate  from  Group  IV  containing  NH4CI  and  NH4OH, 
add  (NH4)2C03.  (If  NH4CI  and  NH4OH  are  not  present,  add 
10  c.c.  of  NH4CI  solution  and  NH4OH  till  strongly  alkaline  before 
proceeding  with  the  analysis.)  Ba,  Sr,  and  Ca  will  be  pre- 
cipitated as  carbonates;  Mg  will  be  held  in  solution  by  the 
ammonium  chlorid.     Filter. 


METALS  OF  GROUP   V. 


6s 


Ca,  Ba,  Sr  carbonates. 


Mg.  and  metals  of  Group  VI. 


Test  the  filtrate  for  Mg  by  adding  Na2HP04,  when  a  white 
crystalhne  precipitate  is  NH4MgP04,6  H2O. 

To  the  carbonates  on  the  paper  add  dilute  acetic  acid, 
which  will  dissolve  the  precipitate,  forming  acetates  of  the  three 
metals. 

Take  a  portion  of  the  acetate  solution  in  a  test-tube  and 
make  a  preliminary  test  for  Ba  by  adding  acid  chromate 
of  potassium  (K2Cr207).  A  yellowish  precipitate  will  be 
BaCr04. 

If  Ba  is  present,  add  K2Cr207  to  the  whole  of  the  solution 
and  filter  out  the  BaCr04. 


BaCr04. 


Sr  and  Ca  acetates,  K2Cr207,  etc. 


It  is  desirable  to  remove  the  excess  of  bichromate  from  the 
filtrate  before  testing  for  Ca  and  Sr.*  To  do  this  add  NH4OH 
till  alkaline;  then  (NH4)2C03  will  precipitate  SrCOs  and  CaCOs. 
Filter  and  dissolve  off  the  paper  with  acetic  acid  as  before. 

*  The  object  of  removing  the  KjCroO?  is  to  furnish  a  colorless  solution  wherein 
the  Sr  or  Ca  precipitates  may  be  more  clearly  discerned.  It  is  not  absolutely 
necessary  and,  in  case  the  amount  of  Sr  and  Ca  is  probably  slight,  might  be  omitted, 
as  the  operation  is  always  attended  with  some  loss. 


66     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 


CaCOs  and  SrCOs,  which  when  treated  with  acetic  acid,  will 


give  a  solution  of  the  acetates  of  Ca  and  Sr. 


Reserve  about  one-fourth  of  this  acetate  solution.  To  the 
remainder  add  dilute  K2SO4  solution,  which  will  precipitate 
SrS04.  (If  only  sHght  amounts  of  Sr  are  present,  it  may  take 
some  time  to  complete  the  precipitation.  If  a  large  amount 
of  Ca  is  present,  some  CaS04  may  also  be  thrown  down.)     Filter. 


SrS04. 


Ca(C2H302)2  or  CaS04. 


Test  filtrate  for  Ca  by  adding  ammonium  oxalate,  which 
will  precipitate  calcium  oxalate,  white. 

If  there  is  any  question  about  the  precipitate  thrown  out 
by  K2SO4  being  Sr,  make  confirmatory  test  on  reserved  portion, 
either  by  flame  test  (page  61),  or  by  adding  CaS04,  and  allow- 
ing to  stand  twelve  hours.  CaS04  will  precipitate  Sr  as  SrS04, 
but  of  course  cannot  precipitate  Ca. 


QUESTIONS  ON  GROUP   V. 
Why    add    NH4CI    before    precipitating    the    group    with 

(NH4)2C03? 

Why   dissolve   the   precipitated   carbonates   in   acetic   acid 
rather  than  HCl? 


METALS  OF  GROUP   V.  67 

Why  use  the  acid  chromate  of  potassium  (K2Cr207)  in 
testing  for  Ba  rather  than  the  neutral  chromate  (K2Cr04)  ? 

Why  precipitate  Sr  and  Ca  after  separation  of  Ba  with 
KzCraOT? 

Laboeatory  Exercise  XVII. 

The  Alkaline  Earths. 

Exp.  30.  To  a  little  clear  lime  water  add  a  few  drops  of 
ammonium  carbonate  solution. 

CaOsHs  +  (NH4)2C03  =  ? 

Will  an  excess  of  reagent  dissolve  this  precipitate?  If  CO2 
were  used  in  place  of  (NH4)2C03  would  the  solubiHty  of  the 
precipitate  be  the  same?     Why? 

Exp.  31.  Take  in  separate  test-tubes  about  5  c.c.  of  each 
of  the  following  dilute  solutions:  CaCl2,  BaCl2,  Sr(N03)2,  and 
MgCl2.  Add  to  each  i  or  2  c.c.  of  NH4CI  solution,  and  then  a 
little  (NH4)2C03  solution. 

Now  add  cautiously  to  each  tube,  containing  a  precipitate, 
dilute  acetic  acid  till  the  precipitates  are  all  dissolved.  To  each 
of  these  three  tubes  add  a  few  drops  of  K2Cr207  solution. 

Write  the  reactions.  Formulate  a  method  for  the  separation 
of  Ca,  Ba,  and  Mg  from  a  mixture  containing  all  three. 

Exp.  32.  To  a  solution  of  magnesium  chlorid  add  a  Httle 
NH4OH  and  NH4CI  solution  and  lastly  some  sodium  phosphate. 

The  formula  for  the  precipitate  is  NH4MgP04.  Complete  the 
reaction. 

MgCl2  +  Na2HP04  +  NH4OH  = 

Exp.  33.  To  each  of  the  four  solutions  used  in  Exp.  31  add 
a  Httle  dilute  H2SO4. 

Which  of  the  four  metals  forms  the  least  soluble  sulphate  ? 

Which  the  most  soluble  ? 

Exp.  34.  To  a  solution  of  Sr(N03)2  add  a  solution  of  CaS04 
and  allow  to  stand. 


68     SALTS  OF  THE  METALS  AND  QUALITATIVE  ANALYSIS 

Exp.  35.  To  a  solution  of  a  calcium  salt  add  some  ammo- 
nium oxalate  solution.    Write  reaction. 

Exp.  36.  In  a  watch  glass  place  a  few  drops  of  lime-water, 
in  another  place  some  baryta  water.  Set  the  two  glasses  aside 
for  a  while  and  explain  any  change  that  takes  place. 

Exp.  37.  Make  flame  tests  with  solutions  of  barium,  stron- 
tium, and  calcium. 

Laboratory  Exercises  XVIII,  XIX,  and  XX. 

Unknown  solutions.  Metals  of  the  various  groups  thus  far 
considered. 


CHAPTER  VIII. 
METALS   OF   GROUP   VI. 

The  Alkaline  Metals,  K,  Na,  NH,  Li. 

Potassium,  sodium,  and  the  hypothetical  "metal"  ammo- 
nium are  the  bases  of  a  very  large  number  of  salts  used  in  the 
arts  and  sciences. 

As  a  class  the  metals  may  be  distinguished  from  the  alkaline 
earths  by  the  ready  solubility  of  their  hydrates  and  carbonates. 
The  hydrates  of  the  alkahne  earths  are  only  sparingly  soluble, 
and  their  carbonates  are  insoluble. 

The  salts  of  lithium  are  also  soluble,  but  are  used  in  relatively 
small  amounts. 

These  bases  are  not  precipitated  by  any  group  reagent  and 
must  be  detected  by  individual  tests. 

Potassium,  K  (Kalium). 

Atomic  weight  39.15.  Occurs  as  carbonate  in  wood  ashes, 
as  nitrate  in  the  "nitre  beds"  of  India,  etc.,  as  chlorid  from  the 
Stassfurt  deposit  in  the  Province  of  Saxony,  Prussia,  as  the 
mineral  sylvite,  also  in  the  double  chlorid  of  Mg  and  K  (car- 
nallite) . 

The  salts  of  potassium  are  generally  soluble  in  water.  Among 
the  more  important  compounds  is  the  hydroxid  KOH.  This 
is  used  very  largely  as  a  starting  point  in  the  preparation  of 
many  of  the  medicinal  salts  of  potassium.  It  may  be  made  by 
treating  potassium  carbonate  with  slaked  lime,  according  to  the 
following  reaction: 

Ca02H2  +  K2CO3  =  CaCOs  +  2  KOH. 

69 


70     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

The  carbonate  obtained  from  wood  ashes  is  known  as  salts 
of  tartar,  and  in  the  impure  form  as  pearl  ash.  Potassium  car- 
bonate is  also  made  in  large  quantities  from  the  native  chlorid 
found  in  the  Stassfurt  deposit. 

The  bicarbonate  KHCO3,  or  saleratus,  may  be  obtained  by 
saturating  the  carbonate  with  CO2. 

K2CO3  +  CO2  +  H2O  =  2  KHCO3. 

This  salt,  used  in  cooking,  proves  more  or  less  irritating,  and  has 
been  practically  replaced  by  the  corresponding  sodium  salt, 
NaHCOa  or  "cooking  soda." 

Potassium  nitrate,  KNO3,  also  called  nitre  and  saltpeter  is 
used  in  medicine  as  a  diuretic.  It  gives  off  oxygen  easily,  and 
is  consequently  a  good  oxidizing  agent,  and  as  such  is  a  con- 
stituent of  fireworks,  gunpowder,  etc. 

KNO3  may  be  prepared  from  the  cheaper  sodium  nitrate  by 
double  decomposition  with  potassium  chlorid. 

NaNOs  +  KCl  =  KNO3  +  NaCl. 

Potassium  bromid,  used  as  a  sedative,  may  be  prepared  by 
treating  caustic  potash,  KOH,  with  bromin. 

6  Br  -t-  6  KOH  =  5  KBr  +  3  H2O  -\-  KBr03. 

The  bromate,  KBr03,  is  separated  by  crystallization. 

Potassium  iodid  may  be  made  in  a  similar  manner  by  sub- 
stituting iodin  for  the  bromin.  Potassium  iodid  is  very  sol- 
uble, being  dissolved  in  less  than  its  own  weight  of  water. 
In  the  laboratory  potassium  iodid  is  used  as  a  solvent  for  iodin, 
and  as  a  reagent. 

Potassium  cyanid,  KCN,  an  extremely  poisonous  compound, 
is  used  by  jewelers  for  cleaning  silver,  etc.,  and  in  the  arts  for 
the  preparation  of  double  salts  used  in  electro-plating.  It  is 
decomposed  by  CO2,  forming  K2CO3  and  Hberating  hydrocyanic 
acid. 

Potassium  chlorate  may  be  prepared  by  treating  a  hot  solution 


METALS  OF  GROUP    VI  7 1 

of  the  hydroxid  with  chlorin  gas.  The  reaction  is  the  same 
as  that  given  for  the  preparation  of  the  bromid,  and  results 
in  five  molecules  of  the  potassium  chlorid  to  one  of  the  chlorate. 

Potassium  sulphid,  K2S,  is  soluble  in  water  and  in  common 
with  other  alkahne  sulphids,  is  a  solvent  for  sulphur,  thereby 
forming  a  number  of  poly  sulphids. 

The  pentasulphid,  K2S5,  is  known  as  liver  of  sulphur  or 
sulphuret  of  potassium. 

Potassium  platinic  chlorid,  K2PtCl6,  and  potassium  acid 
tartrate,  KHC4H4O6,  are  only  sparingly  soluble  and  may  be 
precipitated  by  addition  to  the  solution  of  an  equal  volume  of 
alcohol,  in  which  they  are  quite  insoluble. 

The  potassium  acid  tartrate,  or  bitartrate,  is  also  called 
cream  of  tartar,  and  is  used  in  the  manufacture  of  baking  powder. 
This  salt  separates  from  wine  vats,  it  being  precipitated  by  the 
alcohol  produced  during  the  process  of  fermentation  of  the 
grape  juice.  In  this  impure  form  it  is  known  as  argols,  or 
crude  tartar. 

Analytical  Reactions.  —  The  presence  of  potassium  salts 
may  be  detected  spectroscopically  or  by  the  violet  color  given 
to  the  flame  observed  through  blue  glass.  Make  comparative 
tests  with  known  solutions  of  sodium  and  potassium  salts,  using 
blue  glass  of  sufficient  thickness  to  obscure  the  yellow  (Na)  ray. 

Note.  —  In  making  the  flame  test  the  best  results  are  obtained  by  evaporating  a 
little  of  the  original  solution  to  dryness,  moistening  with  HCl  and  then  taking 
up  on  a  loop  of  clean  platinum  wire. 

The  platinic  chlorid  test  may  be  made  as  follows: 
Add  a  few  drops  of  HCl  to  a  little  of  the  solution,  then 
evaporate  to  dryness.  Keep  at  a  low  red  heat  till  all  ammo- 
nium salts  have  been  driven  off,  cool,  and  take  up  in  a  little 
(not  more  than  5  c.c.)  distilled  water.  Add  a  few  drops  of 
H2PtCl6  and  about  5  c.c.  of  alcohol.  Set  aside  for  some  time. 
K2PtCl6,  yellow,  will  crystalHze  out  recognizable  under  the 
microscope  (Plate  III,  Fig.  3). 


72     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Sodium,  Na  (Natrium). 

Atomic  weight  23.05.  Occurs  principally  as  chlorid  in  sea- 
water  and  in  mineral  deposits,  and  to  a  lesser  extent  as  nitrate, 
Chili  saltpeter,  and  as  cryoHte,  the  double  fluorid  of  Al  and  Na, 
(NasAlFe),  found  in  Greenland. 

Compounds.  —  Sodium  peroxid,  or  dioxid,  Na202,  may  be 
prepared  by  simply  heating  metalHc  sodium  in  dry  air.  It  is  a 
yellowish  white  powder  used  somewhat  in  dental  practice  for 
the  preparation  of  alkahne  solutions  of  H2O2 : 

Na202  +  2  H2O  =  2  NaOH  +  H2O2. 

The  alkahne  peroxid  is  much  more  efficient  as  a  bleaching  agent 
than  the  neutral  or  acid  preparations. 

Sodium  hydroxid,  NaOH,  is  found  in  trade  in  several  forms. 
The  stick  "caustic  soda,"  used  in  chemical  laboratories,  contains 
an3rw"here  from  5  to  30  per  cent  of  water.  In  a  powder  form, 
less  pure  than  the  above,  it  is  known  as  "concentrated  lye," 
Babbitt's  potash,  etc.,  and  is  used  for  cle.aning,  and  in  the  manu- 
facture of  soap.  NaOH  is  caustic  or  escharotic  in  its  action  upon 
animal  tissue.  It  may  be  made  experimentally  by  experiment 
No.  39,  page  78. 

Sodium  carbonate,  Na2C03,  crystalhzes  with  ten  molecules 
of  water.  In  this  form  it  is  known  as  "sal  soda,"  or  washing 
soda.  It  is  used  as  a  starting  point  in  the  manufacture  of  other 
sodium  salts.  Sodium  carbonate  is  produced  from  NaCl  by 
the  LeBlanc  process,  in  which  the  following  reactions  are  in- 
volved : 

(i)  2  NaCl  -f  H2SO4  =  Na2S04  +  2  HCl. 

(2)  Na2S04  +  2  C  =  NaoS  +  2  CO2. 

(3)  Na2S  +  CaCOs  =  NaaCOs  +  CaS. 

The  last  two  reactions  are  combined  in  the  actual  process  of 
manufacture,  and  the  mixture  of  sodium  sulphate,  carbon,  and 
calcium  carbonate  are  heated  together  with  the  resulting  forma- 


METALS  OF  GROUP    VI.  75, 

tion  of  "black  ash"  from  which  is  produced  pure  sodium 
carbonate. 

More  recent  processes  are  the  Solvay  or  Ammonia  process^ 
depending  on  the  following  reaction: 

NaCl  +  NH3  +  CO2  +  H2O  =  NaHCOs  +  NH4CI. 

and  the  cryolite  process  in  which  the  source  of  the  sodium  is  the 
double  fiuorid  of  sodium  and  aluminum,  NasAlFe.  By  this 
process  the  cryolite  is  heated  with  Hme,  forming  calcium  fiuorid 
and  sodium  alummate. 

NasAlFs  +  3  CaO  =  3  CaFa  +  NagAlOs. 

Note.  —  According  to  Remsen  the  sodium  aluminate  probably  consists  of  a 
variety  similar  in  composition  to  the  potassium  aluminate  given  on  page  46, 
(NaA102  and  Na20  until  water  is  added). 

Sodium  bicarbonate,  NaHCOs,  also  called  cooking  soda,  is 
largely  used  like  "saleratus"  (KHCO3)  as  a  source  of  CO2  in  the 
leavening  or  aerating  of  bread. 

Sodium  bicarbonate  is  hydrolized  by  water,  i.e.,  it  dissociates 
in  solution  forming  NaOH  and  H2CO3.  The  carbonic  acid  is  a 
weak  -acid  furnishing  very  few  hydrogen  ions,  while  the  hydroxid 
is  a  strong  base.  It  follows  that  the  reaction  of  such  a  solution 
is  alkaline  to  litmus,  although  the  salt  answers  to  our  definition 
of  an  acid  salt.  This  is  true  of  NaaCOs  (the  products  of  dis- 
sociation being  NaOH  and  NaHCOa) ,  and  in  a  similar  manner  of 
corresponding  potassium  salts. 

Sodium  chlorid,  NaCl,  common  salt,  exists  in  sea-water  to 
the  extent  of  2.7%,  and  is,  to  some  extent,  obtained  from  this 
source,  although  the  greater  amount  is  produced  by  the  salt  mines. 
Salt  is  a  constituent  of  all  of  the  body  fluids,  and  can  be  easily 
obtained  as  cubical  crystals  by  the  evaporation  of  urine  or  of 
dialyzed  saliva. 

Physiological,  or  normal  salt  solution,  contains  about  0.7% 
NaCl,  and  has  practically  the  same  osmotic  pressure  as  blood. 


74     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

The  term  "physiological"  is  to  be  preferred  to  the  term 
''normal, "  as  normal  salt  solution  is  also  properly  applied  to  a 
solution  used  in  volumetric  analysis  containing  exactly  5.85% 
NaCl  (see  page  149). 

Sodium  nitrate,  NaNOs,  Chili  saltpeter,  is  valuable  as  a  ferti- 
lizer, but  too  hygroscopic  to  be  used  in  the  same  way  as  potas- 
sium nitrate,  in  the  preparation  of  gunpowder,  fireworks,  etc. 

Sodium  phosphate,  trisodic  phosphate,  Na3P04,  is  a  crystal- 
line salt,  soluble  in  water,  but  of  sHght  interest  in  Dental  Chem- 
istry. It  is  easily  decomposed  by  CO2,  forming  Na2HP04  and 
NaaCOs. 

2  Na3P04  +  H2O  +  CO2  =  2  Na2HP04  +  NaaCOa. 

The  disodic  phosphate,  Na2HP04,  also  called  neutral  or 
orthosodium  phosphate,  is  the  sodium  phosphate  of  the  Pharma- 
copoeia. It  is  faintly  alkahne  in  reaction,  and  exists  in  the  body 
fluids  generally.  The  alkaline  reaction  (to  litmus)  of  saHva 
is,  in  part,  due  to  its  presence. 

The  acid,  or  monobasic  sodium  phosphate,  NaH2P04,  is  a 
translucent  crystalline  salt  found  to  some  extent  in  the  body 
fluids,  particularly  the  urine,  to  the  acidity  of  which  it  is  prob- 
ably a  contributing  factor,  although  to  a  much  less  extent  than 
was  formally  supposed. 

Sodium  potassium  tartrate,  KNaC4H406,  Rochelle  salt,  is 
used  in  medicine  as  a  mild  laxative.  It  is  the  product  of  the 
double  decomposition  incident  to  raising  bread  with  "cream  of 
tartar  and  soda." 

KHC4H4O6  4-  NaHCOs  =  KN2C4H4O6  +  CO2  +  H2O. 

Sodium  sulphate  crystalUzed  with  ten  molecules  of  water 
(Na2S04io  H2O)  is  known  as  Glauber's  salt. 

Analytical  Reactions.  — -Na  may  be  detected  by  the  use  of 'the 
spectroscope  or  by  the  persistence  of  the  yellow  flame  obtained 
with  a  clean  platinum  wire  and  a  colorless  Bunsen  flame.  Make 
a  comparative  test  with  small  amount  of  known  sodium  salt. 


METALS  OF  GROUP   VI.  75 

Sodium  salts  are  soluble  with  only  a  very  few  exceptions. 
The  pyroantimonate,  Na2H2Sb207,  may  be  precipitated  in  the 
cold  by  a  freshly  prepared  solution  of  potassium  pyroanti- 
monate.    (Prescott  and  Johnson,  p.  228.) 

From  a  solution  stronger  than  3%  and  nearly  neutral  the 
double  acetate  of  uranyl  and  sodium  (NaC2H302,U02(C2H302)2) 
may  be  precipitated.  (Plate  IV,  Fig.  6.)  As  triple  crystalline 
acetates  may  also  be  formed  with  Mg,  Cu,  Fe,  Ni,  and  Co,  it 
is  recommended  to  first  precipitate  the  bases  of  the  first  five 
groups  and  drive  off  ammonium  salts,  as  in  the  test  for  K  with 
HaPtCle.* 

Lithium,  Li. 

Atomic  weight  7.03.  The  carbonate,  citrate,  bromid  and 
chlorid  are  used  in  medicine. 

The  value  of  Hthium  salts  as  uric  acid  solvents  is  question- 
able, because  of  the  insolubihty  of  the  phosphate  (page  237). 

The  presence  of  Hthium  is  easily  shown  after  the  precipita- 
tion of  strontium  by  the  intense  carmine  color  given  to  the 
Bunsen  flame. 

The  spectroscope  furnishes  a  very  delicate  and  positive  test 
for  this  element. 

Ammonium,  NH4. 

Ammonia  is  obtained  in  large  part  from  the  ammoniacal 
liquor  of  the  gas  works,  where  illuminating  gas  is  made  by  the 
distillation  of  coal.  The  liquor,  charged  with  ammonia,  is 
treated  with  hydrochloric  or  sulphuric  acid,  thus  producing  an 
impure  salt  which  is  subsequently  purified  or  used  as  a  source 
of  NH3  in  the  preparation  of  pure  ammonium  compounds. 

(NH4)2S04  +  CaOzHz  =  CaS04  +  2  NH3  +  2  H2O. 

*  Behrens's  Manual  of  Microchemical  Analysis,  page  32. 


76     SALTS  OF    THE   METALS  AND  QUALITATIVE  ANALYSIS 

Compounds.  —  Ammonium  hydroxid,  NH4OH,  has  never 
been  separated  as  such,  free  from  water.  It  undoubtedly  ex- 
ists, however,  in  aqueous  solutions  of  ammonia  gas. 

NH3  +  H2O  =  NH4OH. 

The  negative  hydroxyl  ions  of  this  ammonium  base  do  not  dis- 
sociate to  the  same  degree  as  takes  place  in  solutions  of  KOH; 
hence,  it  is  a  weaker  base. 

Aqua  ammonia  of  the  pharmacopoeia  contains  10%  NH3. 
The  "stronger  water  of  ammonia"  contains  28%  of  the  gas, 
which  is  about  as  strong  a  solution  as  it  is  safe  to  make  for 
shipment,  and  containers  should  never  be  more  than  four- 
fifths  full.  The  28%  solution  is  referred  to  as  26°  ammonia, 
the  degree  indicating  the  specific  gravity  as  taken  by  the  Baume 
hydrometer. 

Ammonium  carbonate  exists  in  solution.  The  salt  used  in 
medicine  under  this  name  is  really  a  mixture  of  ammonium 
bicarbonate,  NH4HCO3,  and  the  carbamate,  NH4NH2CO2. 

This  salt  gives  off  NH3  gas,  and  moistened  with  ammonia 
water  and  perfumed  constitutes  "smelling  salts." 

Ammonium  chlorid,  sal  ammoniac  (NH4CI),  white  crystal- 
Kne,  is  made  by  neutralizing  NH4OH  with  hydrochloric  acid. 
Ammonium  chloride  will  sublime  unchanged.  It  is  freely  sol- 
uble in  water,  and  its  solution  acts  as  an  electrolyte  and  will 
dissolve  metals  from  an  alloy.  If  a  silver  spoon  or  a  lo-cent 
piece  is  allowed  to  remain  for  10  or  12  hours  in  a  dilute 
solution  of  NH4CI,  an  appreciable  amount  of  copper  will  pass 
into  solution,  coloring  it  blue  or  green,  according  to  the  con- 
centration of  the  copper  solution.  It  also  dissolves  some  me- 
talhc  oxides,  as  ZnO. 

As  saliva  is  known  to  contain  considerable  NH4CI,  the 
above  facts  should  be  studied  carefully  in  considering  the  action 
of  saliva  on  substances  used  for  filling  teeth,  although  the  solvent 
action  of  NH4CI  in  sahva  is  nothing  like  what  it  is  in  water. 


METALS  OF  GROUP    VI.  'J'J 

Ammonium  nitrate,  NH4NO3,  crystallizes  in  large  six-sided 
prisms  without  water  of  crystallization.  It  is  very  soluble  in 
water.  It  melts  at  165°  C.  Heated  to  210°  C,  it  decom- 
poses into  nitrous  oxid  and  water.  Above  250°  C,  other  oxids 
of  nitrogen  are  produced,  so  in  the  preparation  of  nitrous  oxid  for 
dental  anesthesia,  care  should  be  taken  to  keep  the  temperature 
of  the  reaction  between  these  Hmits. 

Ammonium  acetate,  NH4C2H3O2.  A  solution  of  this  salt, 
containing  about  7%,  is  used  in  medicine  as  a  diaphoretic. 
The  solution  is  also  known  as  Spirit  of  Mindererus.  In  analyti- 
cal chemistry,  it  is  used  as  a  solvent  for  lead  sulphate. 

Ammonium  sulphate,  (NIl4)2S04,  is  a  white  crystalline  salt 
soluble  in  water,  not  used  medicinally,  but  largely  used  as  a 
reagent  in  physiological  chemistry.  It  melts  at  140°  C,  and 
at  a  higher  temperature  it  decomposes. 

Ammonium  sulphid,  (NH4)2S,  is  used  as  a  solvent  and 
reagent.  It  may  be  prepared  by  saturating  ammonia  water, 
NH4OH,  with  H2S,  then  adding  an  equal  volume  of  ammonia 
water: 

NH4OH  +  H2S  =  NH4SH  -f  H2O, 

and  NH4SH  -f  NH4OH  =  (NH4)2S  -f  H2O. 

A  polysulphid,  made  by  dissolving  sulphur  in  (NH4)2S  is 
the  reagent  used  in  dissolving  the  sulphids  of  Group  II  (b)  and 
in  precipitating  the  zinc  group. 

Ammonium  phosphates.  Ammonium,  Hke  other  univalent 
bases,  is  capable  of  forming,  with  phosphoric  acid,  three  differ- 
ent salts.  (NH4)3P04  is  very  unstable.  The  diammonium 
phosphate  has  been  used,  to  a  slight  extent,  in  medicine  (BrP) 
and  has  been  shown  to  be  an  energetic  activator  of  lactic  acid 
organisms.* 

The  importance  of  this  fact,  in  relation  to  dental  caries,  has 
yet  to  be  demonstrated. 

*  Dr.  Percy  Howe  in  Dental  Cosmos,  Jan.,  1912. 


78     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Microcosmic  salt  is  a  name  given  to  a  double  ammonium  so- 
dium phosphate  (NH4NaHP04-4  H2O)  used  in  blowpipe  analysis. 

Analytical  Reactions.  —  Ammonium  salts  are  generally  sol- 
uble. H2PtCl6  precipitates  the  double  chlorid  (NH4)2PtCl6, 
similar  in  appearance  and  crystalline  form  to  the  corresponding 
potassium  salt  (Plate  III,  Figs.  1-3). 

Ammonium  salts  are  most  easily  detected  by  the  evolution 
of  ammonia  gas  (NH3)  whenever  they  are  heated  with  fixed 
alkah,  NaOH  or  KOH. 

The  test  may  be  made  upon  the  original  solution  by  boiling 
in  a  test-tube  with  a  Httle  10%  NaOH,  and  the  escaping  NH3 
may  be  detected  by  the  odor  or,  better,  by  suspending  in  the 
upper  part  of  the  tube  a  piece  of  moistened  red  litmus  paper,* 
which  is  promptly  turned  blue  by  the  "volatile  alkali."  The 
litmus-paper  test  is  more  delicate  than  the  odor  test.  Care 
should  be  taken  that  the  paper  does  not  touch  the  sides  of  the 
tube,  as  it  may  come  in  contact  with  traces  of  NaOH. 

Many  ammonium  solutions  give  off  NH3  gas  without  the 
aid  of  any  fixed  alkali.  Common  examples  are  the  carbonate, 
acid  carbonate,  hydrate,  sulphid,  and  sulphydrate. 

Laboratory  Exercise  XXL 
The  Alkali  Metals. 

Exp.  38.     In  10  or  15  c.c.  of  water  contained  in  a  porcelain 
dish,  dissolve  a  small  piece  of  metallic  potassium. 
I      Stand  well  away  from  the  dish  as  the  reaction  may  result  in 
spattering  hot  water  or  hot  metal. 

Test  resulting  solution  with  red  litmus  paper.  Write  reac- 
tion. 

Exp.  39.  Take  a  little  strong  solution  of  carbonate  of  soda 
(about  20%  of  crystallized  salt),  heat  nearly  to  boiling  in  a 
porcelain  dish,  then  add  about  half  as  much  milk  of  lime  (made 

*  Blue  paper  may  be  reddened  by  leaving  it  a  few  hours  in  a  wide-mouth 
bottle  after  wetting  the  under  side  of  the  stopper  with  a  drop  or  two  of  acetic  acid. 


METALS  OF  GROUP    VI.  79 

of  one  part  Ca(0H)2  to  four  parts  water).  Continue  the  boil- 
ing for  several  minutes,  then  allow  to  settle.  Decant  the  clear 
liquid. 

Test  the  liquid  with  various  indicators.  Is  it  acid  or  alka- 
line? 

To  a  small  portion  of  it  add  a  few  drops  of  HCl.  Does  it 
effervesce?  Test  in  a  similar  manner  the  carbonate  of  soda 
solution 

NasCOs  +  CaHaOz  =  ? 

Which  of  these  two  compounds  used  is  a  base  ? 

Which  an  alkali? 

Exp.  40.     In  separate  test-tubes  heat  the  following  mixtures: 

1.  Solution  of  NH4CI  and  solution  of  NaOH. 

2.  Solution  of  (NH4)2S04  and  solution  of  KOH. 

3.  Dry  NH4CI  and  dry  CaOsHs. 

In  each  case  note  the  odor  of  the  gas  evolved  and  test  the 
VAPOR  with  moistened  red  litmus  paper  and  write  the  reaction. 

Exp.  41.  Take  three  test-tubes  and  into  one  put  about 
5  c.c.  of  a  dilute  solution  NaCl;  into  the  second,  KCl;  and  into 
the  third,  NH4CI;  then  to  each  add  a  few  drops  of  platinic 
chlorid  solution  and  allow  to  stand  till  the  next  exercise. 

Exp.  42.  Make  flame  tests  according  to  directions  given  in 
the  lecture  room,  with  salts  of  sodium,  potassium,  and  lithium. 

Exp.  43.  Place  in  an  ignition  tube  one  or  two  grams  of 
potassium  tartrate  and  heat  till  no  further  change  takes  place. 
Cool  and  dissolve  in  water.  Test  a  portion  of  the  resulting 
solution  with  a  few  drops  of  HCl.  In  like  manner  test  the 
original  tartrate. 

Note.  —  In  general,  the  ignition  of  salts  of  organic  acids  results  in  the  for- 
mation of  carbonates. 

Exp.  44.  Make  a  spectroscopic  examination  of  solutions  of 
Na,  K,  Li,  Ba,  Sr,  and  Ca,  and  describe  the  bands  observed. 


8o     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Note.  —  This  experiment  is  only  to  be  performed  mider  the  direction  of  an 
instructor.  Opportunity  will  be  given  for  this  experiment  during  the  next  exer- 
cise if  necessary. 

Laboratory  Exercises  XXII  and  XXIII. 

Analyses  of  Solutions  Containing  all  Bases. 

Analysis  of  Groups  III,  IV,  and  V. 

When  phosphates,  borates,  or  oxalates  are  present. 

To  the  filtrate  from  Group  II  add  NH4CI  and  NH4OH  in 
slight  excess.  Heat  to  boiling  and  add  (NH4)2S  slowly  (always 
keeping  the  solution  at  the  boiling-point)  until  precipitation  is 
complete.  Filter  as  rapidly  as  possible  and  wash  with  hot 
water,  adding  occasionally  a  little  (NH4)2S. 

The  filtrate,  which  may  contain  the  barium  and  potassium 
groups,  must  be  concentrated  by  evaporation,  filtered  if  neces- 
sary, and  set  aside.*  The  precipitate  may  contain  MnS,  ZnS, 
CoS,  NiS,  FeS,  A1(0H)3,  and  Cr(0H)3  with  phosphates  or 
oxalates  soluble  in  acids  only.  The  color  of  the  precipitate 
will  give  some  indication  of  what  is  present.  Test  the  pre- 
cipitate for  Mn  by  fusing  a  part  with  KNO3  and  Na2C03. 

Treat  the  precipitate  with  cold  dilute  HCl  in  which  CoS 
and  NiS  alone  are  insoluble.  Filter.  Treat  insoluble  residue 
for  Co  and  Ni  according  to  directions  on  page  56. 

The  HCl  solution,  which  may  contain  Mn,  Zn,  Fe,  Cr,  and 
Al  as  chlorids,  and  phosphates  and  oxalates  soluble  in  acids,  and 
which  is  green  or  violet  if  much  Cr  is  present,  is  boiled  with  a 
few  drops  of  HNO3  until  all  the  H2S  is  expelled. 

Test  a  small  portion  of  the  solution  for  Fe  exactly  as  in 
analysis  of  Group  III  given  on  page  48.  Of  the  remainder  of 
the  solution  take  about  one-third,  and  add  dilute  H2SO4. 

*  If  Ni  is  present,  the  filtrate  is  frequently  brown  or  black,  since  NiS  is  some- 
what soluble  in  an  excess  of  (NH4)2S,  especially  if  much  NH4OH  is  present.  The 
NiS  may  be  precipitated,  after  evaporation,  by  acidifying  with  HCl. 


METALS  OF  GROUP    VI.  8 1 

A  white  precipitate  may  contain  BaS04,  SrS04,  and  pos- 
sibly CaS04.  Filter,  wash  precipitate,  and  fuse  with  a  mixture 
of  NaaCOs  and  K2CO3, 

Note.  —  The  mixture  of  the  two  carbonates  in  molecular  proportions  fuses  at 
a  lower  temperature  than  either  salt  alone. 

Filter  and  wash  the  carbonates  thus  formed,  dissolve  them 
in  acetic  acid  and  examine  this  solution  for  Ba,  Sr,  and  Ca 
as  directed  under  the  Ba  group.  To  the  filtrate  from  the  pre- 
cipitate produced  by  H2SO4,  or  to  the  solution  in  which  H2SO4 
has  failed  to  give  a  precipitate,  add  three  times  its  volume  of 
alcohol;  Ca,  if  present,  is  precipitated  as  white  CaS04,  and  its 
presence  may  be  confirmed  by  dissolving  the  precipitate  in 
water  and  adding  (NH4)2C204,  which  precipitates  CaC204, 
white. 

To  the  rest  of  the  HCl  solution  add  ferric  chlorid,  carefully, 
till  a  drop  of  the  solution  gives,  when  mixed  with  a  drop  of 
ammonic  hydrate,  a  yellowish  precipitate.  To  the  solution  add 
Na2C03  or  K2CO3  till  the  acid  is  nearly  neutraHzed,  then  add 
excess  of  freshly  precipitated  BaCOs,  and  allow  to  stand  over 
night.     Filter. 


Cr  and  Al  as  hydrates.     (Fe  as  phosphate  or  hydrate  and 
BaCOs.) 


MnCl2,  ZnCla,  and  possibly  members  of  Group  V. 


Transfer  the  precipitate  to  a  small  beaker  and  boil  for 
some  time  with  NaOH  or  KOH.  The  Al  will  be  converted 
into  the  aluminate  KAIO2.  The  phosphate  will  be  more  or 
less  completely  changed  to  potassium  or  sodium  phosphate. 
Filter. 


82     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 


Cr(0H)3,  BaCOs,  etc. 


KAIO2  and  Na2HP04. 


Test  precipitate  for  Cr  as  on  page  48.  Add  HNO3  to  fil- 
trate till  acid,  then  divide  into  two  parts;  test  one  for  P205^ 
with  (NH4)2Mo04. 

Test  the  other  for  Al  by  adding  NH4OH  till  alkaline,  when 
precipitate  will  be  AIPO4,  insoluble  in  acetic  acid. 

To  the  solution  of  Mn  and  Zn  chlorids  add  a  little  HCI 
and  boil.  Then  make  alkahne  with  NH4OH,  add  (NH4)2S, 
warm  slightly  and  filter.  The  precipitate  (MnS  and  ZnS)  may 
be  dissolved  in  cold  dilute  HCI  and  tested  for  Mn  and  Zn  as  in 
analysis  of  Group  IV,  page  56. 

OUTLINE  SCHEME  FOR  ANALYSIS  OF  GROUP  I. 

To  about  one-third  of  a  test-tubefnl  of  the  unknown  solution  add  a  few  drops 
of  HCI. 

Ppt.  =  AgCI,  HgCl,  PbCls.     Add  hot  H2O. 


Residue=AgCl,  HgCl. 
Add  NH-OH. 


Residue = HgCl. 
Test,  page  20. 


Solution =AgCl. 
Test  with  HNO3. 


Solution =PbCl2. 
Test  as  on  page  19. 


METALS   OF  GROUP   VI. 


83 


OUTLINE   SCHEME   FOR  ANALYSIS   OF   GROUP   II. 

To  the  warmed  filtrate  from  Group  I  add  H2S.     A  ppt.  may  be  sulphids  of 
As,  Sb,  Sn,  Au,  Pt,  Cu,  Cd,  Bi,  Hg,  and  Pb. 
Filter  and  treat  with  warm  (NH4)2S. 


Residue  is  Group  II  (0),  page  38,  and  consists 

of  sulphids  of  Cu,  Cd,  Bi,  Hg,  and  Pb. 
Treat  on  paper  c  warm  dil.  HNO3. 


Solution=As,  Sb,  Sn,  Au,  and  Pt.  Reprecipitate 
c  HCl,  filter  and  treat  ppt.  c  strong  (NH4)2C03 
sol. 


Residue 

isHg. 

Dissolve 

in  aqua 

regia  and 

test  c 

SnCl2 

(page  38). 


Solution  Cu,   Cd,    Bi,   and   Pb. 
Add  H2SO4  and  filter. 


Ppt. 

is 

PbSOi 


Solution  is  Cu,  Cd,  and 
Bi.  AddNH40Hand 
filter. 


Ppt.  is 
Bi(0H)3 


Solution  is  Cu  and 
Cd. 


Test  for 
Cue  HA 

and 
K4FeCy6. 

(page  39.) 


Test  for 
CdcKCN 
and  HoS. 


Residue  =  Qh,  Sn,  Au,  and  Pt,  sul- 
phids. Treat  c  cone.  HCl,  dilute 
and  filter. 


Residue. 
Au  and  Pt.      Dissolve 
in  aqua  regia  and  di- 
vide. 


Pt.  I. 

Test  for 

Au  c  FeS04 

(p.  40). 


Pt.  II. 
Test  for 

Pt  c 
NH4CI 
and  alco- 
hol. 


Solution. 

Sb  and  Sn. 
Test  for 
SbcPt 

foil  and  Zn. 


Test  for 
Sn  in  fil- 
trate c 
HgCl2 
(p.  40). 


Solution. 
As.     Make 

Gutzeit's 

or  Fleit- 

mann's 

test  for  As . 

(page  28). 


OUTLINE   SCHEME   FOR  ANALYSIS   OF   GROUPS   III   AND   IV. 

Take  the  clear  solution  in  which  H2S  fails  to  produce  a  precipitate  and  boil 
with  a  few  drops  of  HNO3  till  H2S  is  expelled.     Add  NH4CI  and  NH4OH.     Filter. 


Precipitate^  Gro-ay  III.    Fe,  Al,  and  Cr.    Fuse 
c    NajCOs  and   KNO3.     Boil  c     H2O  and 

filter. 


Residue  = 

Fe.    Test  for 

Fe  c  KCyS 

and 

K4FeCy6 

(page  48). 


Soluiion= Al  and  Cr.     Divide 
solution  and 


Test  for  Al 

with  HCl 

and 

(NH4)2C03 

(page  48) 


Test  for  Cr 
with  acetic 
and  lead  ace- 
tate   (page 
48). 


Solutions^  Groups  IV,  V,  and  VI.  Add  (NH4)2S 
and  precipitate.  Group  IV  —  Co,  Ni,  Mn, 
and  Zn.     Treat  with  cold  dilute  HCL 


Residue  =  Co 
and  Ni.     Make 
borax-bead 
test.     Sepa- 
rate Co  by 
means  of 
KNOn  (page 
S6). 


Soluti.on  =  M.n    and     Zn.      Boil 
and  treat  c  KOH  or  NaOH. 


Precipitate  = 

Mn(0H)2. 

Make  red-lead 

test  for  Mn 

(page  S3). 


Solution  = 

K2Zn02.    Test 

for  Zn  c  H2S 

or  (NH4)2S 

(page  57). 


84     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

OUTLINE  SCHEME  FOR  ANALYSIS  OF   GROUPS  III,  IV,  AND  V. 

(Phosphates,  oxalates,  borates,  etc.,  being  present.) 
To  filtrate  from  Group  II  add  NH4CI  and  NH4OH.     Heat  and  add  (NH4)aS. 
Filter  rapidly. 


Predpitate  =  MnS,  ZnS,  CoS,  NiS,  FeS,  A1(0H)3,  Cr(0H)3,  also  phosphates,  etc., 
solulDle  in  acids  only.  Fuse  part  of  precipitate  and  test  for  Mn  (page  57).  Treat 
remainder  c  cold  dilute  HCl. 


Residue = 

CoS  and 

NiS.    Make 

borax-bead 

test  and 
separate  Co 
if  neces- 
sary, c 
KNO2 
(page  56). 


Solution=M.vi.,  Zn,  Cr,  and  Al.     Divide  solution  into  three  parts  of 
about  1/8,  2/8,  and  s/8,  respectively,  and  treat  as  follows: 


Filtrate, 

members  of 

Ba  and  K 

groups. 


I. 

Test 

small 

portion 

for  Fe 

(page  48). 


II. 
To  second  portion  add  di- 
lute H2SO4. 


Precipitate 
may  be 
BaS04, 
SrS04  or 
CaSOi.  Fil- 
ter, wash, 

fuse  c 
Na2C03  and 
K2CO3.  Dis- 
solve  fusion 
in  HA  and 
analyze  for 
Group  V. 


Solution= 

CaS04. 
Add  alco- 
hol; if  pre- 
cipitate oc- 
curs, filter, 
dissolve  in 
H2O,  and 
test  with 
ammonium 
oxalate. 


III. 
To  third   portion  add  FeCl3  to  combine 
c    H3PO1,   etc.,   then   add    NajCOa  or 
K2CO3,  and  BaCOa  (page  81). 


Precipiiaie  =  Cr,  Al,  Fe,  and 
BaCOs.  Boil  precipitate 
c  NaOH  and  filter. 


Residue^ 
Cr,  BaC03, 

etc.     Test 

for  Cr  as  on 

page  48. 


Solution= 

KAIO,. 
Test  for  Al 
as  on  page 


Soliition= 

Mn  and  Zn. 

Reprecipi- 

tate  Mn 

and  Zn  as 

sulphids, 

and  test 

according  to 

page  56. 


OUTLINE   SCHEME  FOR  ANALYSIS   OF   GROUPS  V  AND   VI. 
To  the  clear  filtrate  from  Group  IV  add  (NH4)2C03. 


Precipitate=Ba,  Sr,  and  Ca.    Add  K2Cr207  if  necessary  to  pre- 
cipitate Ba. 


Precipitate = BaCrOi. 


Solution— St  and  Ca..  Reprecipi- 
tate  Sr  or  Ca  with  (NH4)2C03 
and  test,  or  CaS04.  Remove 
Sr  with  K2SO4  and  alcohol,  and 
test  filtrate  for  Ca  with(NH4)2- 
C2O4  (page  66). 


Soluiion  =  Mg  and  Group  VI. 
Test  for  Mg  with  NaoHPOi 
(page  65).  Make  separate 
tests  for  metals  of  Group 
VI  according  to  pages  71,  74, 
and  78  of  the  text. 


CHAPTER  IX. 
ANALYTICAL   REACTIONS    OF   THE   ACIDS. 


In  the  analytical  processes  thus  far  described  we  have  con- 
sidered only  the  separation  and  detection  of  the  basic  or  metallic 
part  of  the  salt,  that  is,  we  have  analyzed  a  solution  of  ferric 
chlorid  and  found  the  iron  only.  It  is  necessary  to  find  the 
chlorin.  Before  making  any  examination  for  acid,  it  will  be 
possible  to  save  a  considerable  amount  of  both  time  and  labor 
by  first  carefully  considering  what  acids  are  capable  of  forming 
soluble  salts  with  the  bases  which  have  already  been  detected. 
To  facihtate  this  consideration  a  table  of  solubilities  will  be  found 
below  and  on  the  following  page,  by  a  careful  study  of  which  it  will 
be  possible  to  select  such  acids  as  are  most  likely  to  be  present 
in  the  unknown  solution  under  investigation,  and  also  to  neglect 
a  number  of  acids  which,  from  the  solubiHty  of  their  salts, 
together  with  the  character  of  the  solution  (acid,  alkaline, 
neutral  and  aqueous,  or  otherwise),  will  necessarily  be  absent. 


TABLE 

SHOWING 

THE    SOLUBILITY 

OF 

SALTS. 

K 

Na 

NH4 

Mg 

Ba 

Sr 

Ca 

Mn 

Zn 

Co 

Ni 

Fe 

Fe2 

w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 

w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 

w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 

w 

w 
w 
w 
w 

w 
a 
a 

wa 
w 
a 
w 
w 
w 
w 
w 
w 
a 
a 
a 
a 
w 

wa 
w 

wa 

w 
a 

wa 
a 
w 
a 
w 
w 
a 

wa 
w 
w 
a 
w 
a 
a 
i 

w 
w 
a 

w 
a 

wa 
a 
w 
a 
w 
w 

wa 
w 
w 
w 
a 
w 
a 
a 
i 

w 
w 
a 

w 

a 

a 

a 

w 

a 

w 

w 

wa 

w 

w 

w 

a 

w 

a 

a 

wi 

w 

w 

a 

w 
a 
a 
a 
w 
a 
w 
w 
w 
a 
w 
w 
a 
a 
a 
a 
w 
a 
w 
wa 

w 
a 

a 
w 
a 
w 
w 
w 
a 
w 
w 
a 
a 
a 
a 
w 
a 
w 
a 

w 
a 
a 
a 
w 
a 
w 
w 
a 
ai 
w 
w 
a 
a 
a 
a 
w 
a 
w 
w 

w 
a 
a 
a 
w 
a 
w 
w 
a 
ai 
w 
w 
a 
a 
a 
a 
w 
a 
w 
a 

w 
a 
a 
a 
w 
a 
w 
w 

ai 
w 
w 
a 
a 
a 
a 
w 
a 
w 
wa 

w 

a 

Arsenite 

Borate 

Bromid 

a 
a 
w 
a 

Chlorate 

Chlorid 

Chromate 

w 
w 
w 

lodid 

w 

w 

a 

Oxid             

a 

Phosphate 

a 

Silicate 

a 

w 

a 

Sulphocyanate 

Tartrate 

w 
w 

85 


86     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 


TABLE   SHOWING  THE   SOLUBILITY  OF   SALTS.—  CONCLUDED 


Cd 


Acetate 

Arsenate 

Arsenite 

Borate 

Bromid 

Carbonate .... 

Chlorate 

Chlorid 

Chromate. ... 

Cyanid 

lodid 

Nitrate 

Oxalate 

Oxid 

Phosphate 

Silicate 

Sulphate 

Sulphid 

Sulphocyanate 
Tartrate 


Cr2 

AI2 

Sb 

Sn" 

Sniv 

Au 

Ag 

Hg2 

Hg 

Pb 

Bi 

Cu 

w 

w 

w 

w 

w 

wa 

wa 

w 

w 

w 

w 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

w 

w 

wa 

w 

w 

w 

1 

ai 

wa 

wi 

wa 

w 

a 

a 

a 

a 

a 

a 

w 

w 

w 

w 

w 

w 

w 

w 

w 

w&i 

w 

wa 

w 

w 

w 

I 

ai 

w 

wi 

wa 

w 

a 

a 

a 

a 

a 

wa 

ai 

a 

w 

a 

w 

1 

w 

a 

wa 

a 

w 

w 

wa 

w 

w 

a 

1 

a 

a 

wa 

a 

a 

w 

w 

a 

a 

w 

w 

w 

w 

a 

w 

w 

a 

a 

a 

w 

a 

a 

a 

a 

a 

a 

a&i 

a&  i 

a 

a 

a&  i 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

ai 

a 

a 

w&a 

w 

a 

w 

w 

wa 

wa 

wa 

1 

a 

w 

a 

a 

a 

a 

a 

a 

a 

a 

a 

a 

w 

w 

1 

a 

w 

a 

a 

w 

w 

w 

wa 

a 

a 

a 

a 

a 

wa 

wa 
wa 


w,  soluble  in  water;  a,  insoluble  in  water,  soluble  in  acids;  i,  insoluble  in  water  or  acids;  wa, 
sparingly  soluble  in  water,  readily  soluble  in  acids;  wi,  sparingly  soluble  in  water  and  acids;  ai, 
sparingly  soluble  in  acids  only. 

In  this  connection  it  is  well  to  remember  that  practically  all 
nitrates  and  chlorates  are  soluble  in  water;  sulphates  are  mostly 
soluble,  except  those  of  barium,  strontium,  and  calcium.  Phos- 
phates (di-  or  trimetallic) ,  silicates,  oxalates,  and  borates  are 
practically  insoluble,  except  those  of  the  alkahne  metals.  This 
latter  statement  is  also  true  of  carbonates,  except  that  some  of 
the  carbonates  will  dissolve  to  an  appreciable  extent  in  water 
containing  CO2.  Chlorids,  bromids,  and  iodids  are  nearly  all 
soluble  except  those  of  the  first-group  metals.  Sulphids  are 
insoluble  except  those  of  Groups  V  and  VI.  Acid  salts  are 
usually  more  soluble  than  neutral  salts. 

In  making  qualitative  tests  for  the  acids  it  is  not  necessary 
to  separate  them  one  from  the  other,  as  it  is  in  the  case  of  metals ; 
hence  the  tests  are  individual  ones,  usually  made  upon  the  origi- 
nal substance  or  solution,  and  often  require  confirmation  before 
conclusive  evidence  is  obtained.  The  grouping  is,  therefore, 
simply  for  convenience,  as  it  thus  becomes  possible  to  exclude  a 
considerable  number  of  acids  by  a  single  general  test. 


ANALYTICAL  REACTIONS  OF   THE  ACIDS  87 

Acid  Groups. 

Group  I  may  include  such  acids  as  give  effervescence  when 
their  dry  salts  are  treated  with  dilute  H2SO4,  as  H2CO3,  H2S, 
H2S2O3,  H2SO3  and  HCN. 

Group  II  may  include  acids  giving  a  precipitate  with  AgNOs 
in  dilute  HNO3  solution,  as  HCl,  HBr,  HI,  HCN,  HCNS,  HNO2, 
HCIO,  H4FeCy6,  H3FeCy6,  H2S2O3,  H2S  and  HPH2O2. 

This  second  group  may  be  further  subdivided  into  three  parts 
according  to  the  color  of  the  precipitate  obtained  (pages  89  and  91). 

Group  III  may  include  acids  forming  insoluble  salts  with 
BaCl2  or  CaCl2  and  not  found  in  Groups  I  or  II,  or  H2SO4,  H2C2O4, 
H3PO4,  H3BO3,  H2Cr04  and  H2Si03. 

Besides  the  acids  found  in  these  groups  there  are  three 
others  of  common  occurrence:  nitric  (nitrates),  chloric  (chlo- 
rates), and  acetic  (acetates). 

Detection  of  Acids  of  Group  I. 

(Acids   effervescing   with    dilute   sulphuric  acid.     H2CO3,   H2S,    H2SO3,   H2S2O3, 

HCN.) 

To  a  test-tube  a  quarter  full  of  the  unknown  solution,  or  a  little 
dry  substance  on  a  watch-glass,  add  dilute  H2SO4.  If  solution  is 
very  dilute,  concentrate  it  before  making  test,  as  a  slight  amount 
of  gas  might  be  absorbed  by  the  water.  Watch  carefully  for 
any  escape  of  gas  and  note  any  odor  which  may  be  given  off. 

Carbonates  evolve  CO2,  odorless,  but  if  passed  into  lime-water 
or  baryta-water  will  give  white  precipitate  of  CaC03  or  BaCOs. 

Sulphids  evolve  H2S,  odor  of  rotten  eggs.  Confirm  by 
adding  a  httle  dilute  H2SO4  to  the  suspected  powder  (or  solu- 
tion) in  a  test-tube  and  holding  over  the  mouth  of  the  tube  a 
piece  of  filter-paper  wet  with  a  solution  of  lead  acetate.  The 
test-tube  may  be  warmed  slightly  to  expel  the  gas,  when  a 
dark-colored  stain  will  appear  on  the  filter-paper,  due  to  the 
formation  of  PbS. 


88     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Sulphites  evolve  SO2,  odor  of  burning  sulphur.  Sulphites 
in  neutral  solution  may  be  further  identified  by  the  deep-red 
color  produced  with  ferric  chlorid.  The  color  is  discharged 
upon  addition  of  dilute  acids,  HCl,  or  H2SO4  (difference  from 
HCyS). 

Thiosulphates  also  evolve  SO2,  but  at  the  same  time  the 
mixture  becomes  cloudy  from  precipitation  of  sulphur.* 

Thiosulphates  in  neutral  solution  treated  with  ferric  chlorid 
give  a  violet  to  purple  color,  fading  (rapidly  upon  warming)  to 
a  colorless  solution.  In  mixtures  of  sulphites  and  thiosulphates 
both  acids  may  often  be  detected  by  the  use  of  FeCls,  the  deep-red 
coloration  of  the  mixed  acids  rapidly  fading  to  the  lighter  red 
of  Fe2 (803)3  (not  to  colorless  solution). 

Cyanids  evolve  HCN,  odor  of  peach-stones.  (Mercuric 
cyanid  does  not  respond  to  this  reaction.)  Confirm  by  reactions 
given  under  Group  II. 

Preliminary  Tests  for  Common  Acids  or  Groups  II  and  III. 

(In  preparatory  courses  the  acids  given  in  this  list  may  be  sufi&cient.) 

From  the  acids  of  Group  II  and  III  it  may  be  desirable  to 
select  for  laboratory  practice,  at  least  at  the  beginning  of  the 
acid  work,  the  more  common  members  of  the  groups.  These 
will  be  HCl,  HBr,  HI,  HCN,  and  H2S  of  Group  II  and  H2SO4, 
H2C2O4,  and  H3PO4  of  Group  III;  and  tests  for  them  may  be 
made  as  follows: 

Chlorids  give  with  AgNOs  in  presence  of  HNO3  a  white 
curdy  precipitate  of  AgCl,  much  more  freely  soluble  in  ammonia 
than  any  other  acid  of  the  group  here  given  except  the  cyanid 
AgCN,  but  HCN  is  a  member  of  the  first  acid  group  and  would 
have  been  previously  detected. 

*  Sulphids  may  also  precipitate  sulphur  in  presence  of  compounds  capable  of 
oxidizing  the  H2S,  such  as  FeCls.  In  the  absence  of  sulphates  either  H2SO3  or 
H2S2O3  can  be  oxidized  to  H2SO4  by  heating  with  HNO3  and  a  precipitate  of  BaS04 
obtained  with  BaCl2. 


ANALYTICAL   REACTIONS  OF   THE  ACIDS  89 

Bromids  with  AgNOs  and  HNO3  give  a  precipitate  of  AgBr 
similar  in  appearance  to  AgCl,  but  with  a  sHghtly  yellowish 
color  and  only  sparingly  soluble  in  NH4OH. 

The  tests,  described  on  page  91,  should  also  be  made  if 
bromids  or  iodids  are  suspected  in  the  solution. 

Cyanids,   see  Group  I. 

Sulphids  will  give  a  black  precipitate  with  AgNOs,  and 
have  been  previously  considered  in  Group  I. 

Sulphates  may  be  detected  by  first  acidifying  the  solution 
strongly  with  HCl  (filtering  out  a  precipitate  if  any  occurs) 
and  adding  solution  of  BaCl2;  a  white  precipitate  will 
then  be  BaS04,  showing  presence  of  sulphates  in  solution 
tested. 

Phosphates  in  a  solution  containing  HNO3  and  free  or 
nearly  free  from  HCl  will  give,  with  ammonium  molybdate, 
a  yellow  crystalline  precipitate  of  ammonium  phosphomolyb- 
date. 

Oxalates  may  be  detected,  in  a  solution  free  from  sul- 
phates and  which  is  slightly  acid  v^^ith  acetic  acid,  by  simple 
addition  of  calcium  chlorid,  which  will  precipitate  CaC204, 
white  and  crystalline. 

Detection  of  Acids  of   Group  II. 

(Giving  precipitate  with  AgNOs  in  presence  of  dilute  HNO3.) 

To  the  solution  to  be  tested  add  a  very  slight  amount  of 
HNO3  and  a  few  cubic  centimeters  of  AgNOs  solution.  A  pre- 
cipitate indicates  acids  of  this  group. 

(a)  If  the  precipitate  is  white,  the  presence  of  chlorids  (HCl), 
cyanides  (HCN),  sulphocyanates  (HCNS),  ferrocyanates 
(H4FeCy6),  hypochlorites  (HCIO),*  or  nitrites  (HNO2)  is  in- 
dicated. 

*  Precipitate  is  AgCI.  Reaction  is  3  NaClO  +  3  AgNOs  =  2  AgCl  +  AgCIOg  + 
3  NaNOs. 


90     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

To  separate  or  identify  these  silver  precipitates  allow  to 
settle,  decant  the  supernatant  fluid,  and  add  NH4OH.  Shake 
thoroughly,  when  the  chloride  (AgCl),  cyanide  (AgCN),  and 
nitrite  (AgN02)  will  dissolve  easily,  the  sulphocyanate  (AgCyS) 
and  the  ferrocyanide  (Ag4FeCy6)  slowly  or  slightly. 

If  HCyS,  or  H4FeCy6  is  indicated,  test  original  solution  with 
a  few  drops  of  FeCls.  Sulphocyanates  or  thiocyanates  (HCNS) 
give  a  deep  blood-red  solution.  The  color  is  soluble  in  ether 
and  may  be  discharged  by  HgCl2.  Ferrocyanids  (H4FeCy6) 
give  a  deep-blue  precipitate.     (See  page  45.) 

Acids  forming  white  silver  and  precipitates,  easily  soluble  in 
ammonia,  may  be  distinguished  as  follows : 

Chlorids  (HCl)  may  be  distinguished  from  HBr  and  HI 
by  the  ready  solubility  of  the  silver  precipitate  in  NH4OH.  If 
bromids  and  iodids  are  present,  Hberate  the  halogens  by  means 
of  Mn02  and  H2SO4  and  pass  the  mixed  gases  into  a  solution  of 
anilin  in  acetic  acid  (4  c.c.  of  saturated  aqueous  solution  of 
anilin  and  i  c.c.  glacial  acetic  acid).  lodin  gives  no  precipi- 
tate, bromin  gives  a  white  one  and  chlorin  a  black  one.  (Prescott 
and  Johnson,  page  336.) 

This  is  a  delicate  and  very  satisfactory  test  for  bromin  but 
not  so  delicate  for  chlorin  in  the  presence  of  bromids.  For 
such  cases  the  following  chloro-chromic  anhydrid  test  is  recom- 
mended. Neutralize  the  solution  if  necessary,  evaporate  to 
dryness,  transfer  residue  to  a  test-tube  of  rather  small  diam- 
eter, add  a  little  soHd  K2Cr207,  then  concentrated  H2SO4.  De- 
cant the  fumes  into  a  wider  test-tube  containing  a  few  centi- 
meters of  NH4OH. 

If  the  chloro-chromic  anhydrid  is  evolved,  ammonium 
chromate  will  be  formed.  Test  by  making  acid  with  acetic 
acid,  then  adding  acetate  of  lead.  A  yellow  precipitate  of  lead 
chromate  indicates  chlorin  in  the  original  solution. 

Hypochlorites  Hberate  I  from  KI  without  the  addition  of 
acid. 


ANALYTICAL   REACTIONS  OF   THE  ACIDS  9 1 

Note.  —  Hypochlorite  solutions  are  usually  quite  strongly  alkaline,  and  in  such 
cases  a  considerable  amount  of  iodid  is  necessary  to  obtain  the  characteristic  color 
in  chloroform  or  with  starch. 

Nitrites  liberate  I  from  KI  after  the  addition  of  acetic 
acid.  They  also  give  a  brown  coloration  with  acetic  acid  and  a 
crystal  of  ferrous  sulphate.     (Nitrates  require  a  stronger  acid.) 

Note.  —  This  test  is  much  more  delicate  than  either  of  the  others  given,  and 
if  the  solution  is  very  dilute  it  is  well  to  make  it,  even  if  the  indigo  color  is  not 
discharged. 

Further  mix  a  little  of  the  solution  with  a  few  cubic  centi- 
meters of  dilute  indigo  solution  and  shake.  The  indigo  is  de- 
colorized by  either  hypochlorites  (HCIO)  or  by  nitrites  (HNO2). 

Cyanids  may  be  tested  for  as  under  Group  I.  If  this  test  is 
not  conclusive,  they  may  be  converted  into  sulphocyanides  by 
the  addition  of  ?P*few  drops  of  (NH4)2S  and  evaporation  on  the 
water-bath  to  dryness.  It  may  then  be  dissolved  in  a  little  dis- 
tilled HoO,  filtered  and  tested  with  FeCls. 

(b)  The  precipitate  is  red-brown  or  orange,  soluble  in 
NH4OH  =  HsFeCye-     Ferricyanid  indicated. 

(c)  The  precipitate  is  black  or  turns  black  upon  warming: 
H2S  turns  black  immediately.  HH2PO2  starts  to  precipitate 
white,  but  rapidly  turns  black,  II2S2O3  precipitates  white  and 
turns  black  slowly  or  upon  heating. 

Sulphids  (HoS)  and  thiosulphates  (H2S2O3)  may  also  be 
detected  as  described  under  Group  I,  Acids. 

{d)  If  the  precipitate,  originally  obtained,  is  yellow  and  in- 
soluble in  NH4OH,  iodids  are  indicated;  if  yellowish  white  and 
slowly  soluble  in  NH4OII,  hromids  are  probably  present. 

Iodids  and  bromids  (HI  and  HBr)  may  be  detected  in 
the  same  solution  by  adding  CI  water,  very  cautiously  at  first, 
and  shaking  with  chloroform.  The  CI  liberates  the  iodin, 
which  is  dissolved  by  the  chloroform  with  violet  color.  Excess 
of  CI  decolorizes  the  iodin  and  liberates  the  bromin,  which,  in 
turn,  is  dissolved  by  the  chloroform  with  yellow  to  red  color. 


92     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

Acid   Group  III. 

(Acids  forming  insoluble  barium  or  calcium  salts,  not  included  in  the  Acid 
Group  I  or  II.) 

The  members  of  this  group  may  be  separated  from  each 
other,  although  this  is  not  necessary  unless  several  members 
are  present.  H2SO4,  H2C2O4,  H2Cr04,  H2Si03,  H3BO3,  H3PO4, 
separated  as  follows:  To  a  little  of  the  unknown  solution  add 
2  or  3  c.c.  of  HCl;  a  white  or  gelatinous  precipitate  which  is  not 
dissolved  by  dilution  with  water  and  warming  is  probably  silicic 
acid.  Make  a  bead  test  with  microcosmic  salt;  the  particles  of 
Si02  remain  undisturbed  by  the  hot  bead,  forming  the  so-called 
silicon  "skeleton."  Filter  out  the  siHcic  acid  and  add  CaCl2 
or  a  mixture  of  BaCl2  and  CaCl2;  a  white  precipitate  will  be 
BaS04*  (test  for  sulphates).  The  Ba  and  Ca  salts  of  all  remain- 
ing acids  of  the  group  being  soluble  in  HCl. 

Filter  out  the  BaS04,  and  to  the  filtrate  add  NH4OH,  which 
will  cause  a  precipitate  of  barium  oxalate,  chromate,  borate,  and 
phosphate.  Filter,  wash  precipitate  two  or  three  times,  reject 
wash-water,  then  transfer  to  test-tube  by  making  a  small  hole  in 
point  of  paper  and  forcibly  washing  through  with  the  least  pos- 
sible amount  of  water;  acidulate  strongly  with  acetic  acid,  which 
will  dissolve  the  phosphates  and  borates,  leaving  undissolved 
the  oxalates  (BaC204,  white)  and  chromates  (BaCr04,  yellow.) 


Oxalic  and  chromic  acids  as  barium  salts. 


Phosphoric  and  boric  acids. 


*  If  the  HCl  is  too  strong,  BaCl2  may  be  precipitated  as  such,  but  the  pre- 
cipitate in  this  case  will  form  more  slowly  than  the  BaS04;  it  will  have  a  crys- 
talline appearance  and  will  dissolve  upon  addition  of  water. 


ANALYTICAL  REACTIONS  OF   THE  ACIDS  93 

Divide  the  filtrate  into  two  parts,  (a)  and  (b).  Test  one 
part,  (a),  for  H3PO4  by  adding  to  it  an  excess  of  ammonium 
molybdate*  (in  HNO3),  when  a  yellow  precipitate  (forming 
sometimes  after  several  hours'  standing)  is  ammonium  phospho- 
molybdate  (test  for  phosphates);  the  mixture  may  be  warmed 
to  hasten  precipitation;  the  degree  of  heat  should  not  exceed 
40°  C,  as  the  ammonium  molybdate  might  be  decomposed, 
giving  a  yellow  precipitate  similar  to  the  phosphomolybdate. 

Note. —  If  As  is  present,  it  must  be  removed  by  H2S  before  testing  for  H3PO4.. 

Test  the  other  part,  (b),  for  H3BO3  by  evaporating  to  dryness 
in  a  porcelain  dish ;  then  moisten  with  strong  H2SO4,  cover  with 
a  little  alcohol,  and  ignite.  Boric  acid  will  give  to  the  flame 
(particularly  the  edge)  of  the  burning  alcohol  a  green  color  due 
to  formation  of  ethyl  borate.  This  color  is  more  easily  apparent 
if  the  dish  is  placed  in  a  darkened  corner. 

A  test  for  H3BO3  may  also  be  made  with  turmeric  paper, 
which  if  dipped  into  a  solution  of  boric  acid,  or  of  a  borate  mixed 
with  HCl  or  H2SO4  to  sHght  but  distinct  acid  reaction,  and  dried 
at  100°,  becomes  red;  the  red  color  becomes  bluish  black  or 
greenish  black  when  moistened  with  a  solution  of  an  alkali  or 
an  alkaline  carbonate.  If  there  is  a  suspicion  that  H2Cr04  and 
H2C2O4  are  both  present,  dissolve  the  precipitate  of  barium 
oxalate  and  chromate  off  the  paper  with  dilute  HCl;  divide  the 
filtrate  into  two  parts  and  test  one  for  H2Cr04  by  addition  of 
H2O2,  which  with  chromates  in  presence  of  HCl  produces  a  deep- 
blue  solution  and  ultimately  CrCla. 

In  the  absence  of  chromates,  the  precipitate  being  white, 
oxalates  may  be  confirmed  by  coloring  the  second  part  of  the 
solution  a  faint  pink  with  a  dilute  solution  of  KMn04  and  warm- 
ing, when  the  color  will  be  discharged. 

In  the  presence  of  chromates,  the  precipitate  being  yellow, 
it  will  be  necessary  to  test  the  original  solution  for  oxalates 

*  Preparation  of  ammonium  molybdate  solution,  appendix  p.  377. 


■94     SALTS  OF   THE  METALS  AND  QUALITATIVE   ANALYSIS 

as  follows:  To  a  few  centimeters  of  the  unknown  add  alcohol; 
warm.  The  chromate  will  be  reduced  to  CrCls.  Add  NH4OH 
till  alkaUne  and  filter  out  the  precipitate,  Cr(0H)3.  The 
filtrate  may  be  tested  for  oxaHc  acid  as  above,  or  with  CaCl2; 
a  white  precipitate  being  CaC204. 

Acids  of  Group  IV. 

The  remaining  acids  of  importance  not  included  in  either 
of  the  three  preceding  groups  are  nitric,  HNO3,  chloric,  HCIO3, 
and  acetic,  HC2H3O2. 

Nitrates.  —  Saturate  5  c.c.  of  a  very  dilute  nitrate  solution 
with  FeS04.  Filter  and  carefully  underlay  the  clear  filtrate 
with  concentrated  sulphuric  acid;  a  dark  ring  (pale  red-brown 
to  nearly  black)  at  point  of  contact  of  the  two  liquids  shows 
presence  of  a  nitrate. 

Chlorates.  —  A  solution  free  from  chlorids  or  hypochlorites 
treated  with  Zn  and  dilute  H2SO4  will  give  a  test  for  HCl  if 
chlorates  were  originally  present,  the  chlorate  having  been  re- 
duced by  the  nascent  H : 

2  KCIO3  +  6  Zn  -f  7  H2SO4  =  6  ZnS04  +  K2SO4  +  2  HCl  -^  6  H2O. 

Boiling  with  sulphurous  acid  also  reduces  HCIO3  (and  HCIO) 
to  HCl. 

If  the  substance  is  in  solid  form,  a  very  small  particle  may 
be  warmed  with  concentrated  H2SO4.  Chlorates  detonate  and 
give  off  yellow  fumes  of  CIO2 : 

3  KCIO3  +  2  H2SO4  =  2  KHSO4  +  KCIO4  +  2  CIO2  +  H2O. 

Acetates  give  with  ferric  chlorid  a  red  color  which  is  not 
discharged  by  HgCl2  (difference  from  sulphocyanate) ,  but  may 
be  discharged  by  HCl  (difference  from  sulphocyanate  and 
meconate) . 

A  more  positive  test  is  the  formation  of  the  ethyl  ester 


ANALYTICAL  REACTIONS  OF   THE  ACIDS  95 

or  acetic  ether.     A  blank  test  for  comparison  should  always 
be  made,  the  method  of  procedure  being  as  follows : 

Take  two  test-tubes  of  practically  equal  diameter,  mix  in 
each  equal  volumes  of  alcohol  and  strong  H2SO4;  warm  the  tubes 
together;  then  into  one  introduce  a  few  centimeters  of  the  un- 
known solution,  and  into  the  other  an  equal  volume  of  H2O. 
Heat  again  to  a  boiling-point  and  compare  the  odors  from  the 
two  tubes.     The  acetate  is  easily  detected  if  present. 

Laboratory  Exercises  XXIV  and  XXV. 
Unknown  Solutions  Containing  Acids  and  Bases  of  Group  VI. 


CHAPTER  X. 
ANALYSIS  IN  THE  DRY  WAY. 

In  the  examination  of  solid  substances  much  may  be  learned 
by  a  few  simple  tests  directly  applied  to  the  substance,  which 
has  been  reduced  (if  necessary)  to  the  form  of  a  powder. 

Some  of  these  are  usually  used  as  preliminary  to  the  solu- 
tion of  the  substance  and  regular  analysis  in  the  wet  way.  These 
tests  may  be  made  quickly,  and,  with  a  little  elaboration,  will 
often  give  all  the  information  required  regarding  an  unknown 
substance. 

The  practical  questions  of  actual  experience  are  usually 
simple  ones.  It  is  not  an  analysis  of  an  unknown  solution 
possibly  containing  all  the  metals  of  one  or  more  groups  that 
interests  an  active  practitioner,  but  a  specific  inquiry  as  to 
whether  or  not  this  or  that  preparation  contains  or  does  not 
contain  the  necessary  or  the  undesirable  ingredient,  whether 
the  thing  is  of  the  composition  or  of  the  strength  represented, 
and  a  few  minutes'  work  in  the  laboratory,  especially  if  aided 
by  the  microscopical  tests  given  in  a  subsequent  chapter,  will 
frequently  be  found  sufficient  to  answer  questions  of  this 
character. 

The  tests  made  in  the  dry  way  are  not  as  delicate,  nor  are 
the  results  obtained  (especially  negative  ones)  as  conclusive,  as 
those  of  a  systematic  analysis  of  the  substance  in  solution,  and 
in  occasional  cases  it  may  be  necessary  to  resort  to  the  more 
tedious  process. 

Before  undertaking  the  analysis  of  a  substance,  note  care- 
fully its  physical  properties  of  odor,  color,  and  solubility;  also 
whether  it  is  magnetic,  metallic,  or  crystalHne. 

96 


ANALYSIS  IN  THE  DRY  WAY  97 

The  volatile  acids,  certain  ammonium  compounds,  bromin, 
and  iodin  may  be  detected  frequently  by  their  odor. 

Colors  of  Salts  and  Solutions. 
The  following  colored  salts  are  soluble  in  water : 

Black Silver  albuminate  (argyrol,  etc.). 

Violet  or  purple Chromic  salts  and  permanganates. 

CrOs  and  acid  chromates,  KsFeCye,  sodium- 


'      nitro-prusside,  H2PtCl6 

Reddish  brown  or  purple-red Manganic  salts. 

Reddish  yellow Ferric  salts  and  AuCla. 

,^  „  C  Neutral  chromates  of  the  alkalies,  salts  of 

Yellow < 

L      uranium. 

Pale  yellow ' K4FeCy6  (Potassium  ferrocyanide). 

Pink Salts  of  cobalt. 

Pale  pink Manganous  salts. 

^  (  Ferrous    salts,  nickel  salts,  certain  copper 

Green <  , 

I      salts. 

Dark  green Some  chromic  salts. 

Blue-green Chromates. 

Blue Cupric  salts. 

The  following  colored  substances  are  insoluble  in  water: 

r  Carbon  and  carbids,  metals,  many  metallic 
Black <      sulphids,  oxids  of  Cu,  Fe,  Mn,  and  Pb. 

'      Iodin  is  bluish  black. 

Red HgO,  HgS,  Rgh,  PbsOi,  AS2S2. 

Brick-red Amorphous  phosphorus,  Fe203. 

Light  brown PbO  (litharge) . 

r  S,  HgO,  CdS,  AS2S3,  Pbl2,  Ag3P04,  ammo- 
Yellow  <      nium  phospho-molybdate,  and  chromates 

'      of  the  heavy  metals,  PbCrO^,  BaCr04. 
p  (  Some  copper  compounds,  CU2I2,  Paris  green, 

(      etc.,  Cr203. 

p.  (  Some   copper   compounds,   Prussian   blue, 

(      ultramarine;  anhydrous  salts  of  cobalt. 


98     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

METHODS   OF   EXAMINATION. 

Powder   the   substance   and   apply   tests   described  in   this 
chapter,  which  will  be  considered  in  the  following  order: 

A.  Ignition  with  free  access  of  air. 

B.  Closed- tube  test. 

C.  Flame  test  on  platinum  wire. 

D.  Examination  with  the  blow-pipe  on  plaster  slab. 

E.  Bead  tests  on  platinum  wire. 

F.  Special  tests,  distinguishing  or  confirmatory. 


A.   Ignition  in  Air. 

This  test  may  be  made  on  a  crucible  cover  or  on  platinum 
foil.  If  there  is  any  probability  of  I,  Br,  CI,  P  or  easily  reduced 
metallic  compounds  in  the  unknown  substance,  the  platinum 
foil  is  likely  to  be  destroyed;  hence,  the  porcelain  is  recommended. 

The  heat  employed  should  be  very  low  at  first;  then  it 
should  be  gradually  increased  and  the  test  carefully  watched. 

The  majority  of  phenomena  occurring  under  A  are  more 
easily  observed  in  the  test  made  with  the  closed  tube,  B,  and 
will  be  given  under  that  head. 


Observed  Phenomena. 
The  substance  melts  and  steam  is  given  off. 


The  substance  burns  (a)  at  comparatively  low 
temperature  with  blue  flame  and  odor  of 
SO2  or  burning  matches. 

(b)  With  yellow  flame  and  much  smoke. 

(c)  Blackens  and  then  burns  at  fairly  high 

temperature,  leaving  white  or  gray  ash. 

(d)  Blackens  without  burning. 

Vapors  are  given  off: 

(a)  Of  a  violet  color. 

(b)  Of  a  red-brown  color. 

(c)  Of  a  greenish-yellow  color. 

(d)  White,  practically  odorless. 


Indications. 

Water  of  crystallization, 
NH4N03orH2C204,  which 
entirely  disappear. 

Sulphur. 


Fat,  waxes,  resins,  etc. 
Carbonaceous  matter  other 

than  fats,  etc. 
Formation  of  oxids  of  Fe, 

Co,  Ni,  or  Cu. 

lodin. 

Br  or  nitrogen  oxids. 
Chlorin  or  CIO2. 
Some      ammonium      salts, 
NH4CI,  (NH4)2S04,  etc. 


ANALYSIS  IN   THE  DRY   WAY 


99 


Observed  Phenomena. 

(e)  White  with  odor  of  NH3. 
(/)  White  with  odor  of  garlic, 
(g)  White  and  yellow  with  ammoniacal  or 
empyreumatic  odor. 
The  substance  decrepitates. 

Examine  residue  on  foil  (porcelain) ;   add  a  drop 
or  two  of  water  and  test  with  litmus-paper. 
If  found  to  be  acid. 
If  alkaline  without  blackening. 

If  alkaline  with  blackening. 


Add  a  drop  of  dilute  HCl,  effervescence. 


Indications. 

Ammonium  carbonate. 

Arsenic. 

Organic  matter. 

Water  held  mechanically  by 
crystals,  as  NaCl,  etc. 


Acid  salts. 

Fixed  alkali  hydrates  or 
carbonates. 

Carbonate  formed  by  com- 
bustion of  organic  com- 
pounds. 

Carbonates. 


B.   Closed-tube  Test. 

Select  a  tube  of  soft  glass  about  5  or  6  inches  in  length. 
Seal  one  end  and  enlarge  sHghtly.  Into  the  bulb  thus  formed 
introduce  a  few  grains  of  the  unknown  powdered  substance. 
Heat  carefully,  making  the  following  tests  at  various  stages  of 
the  process.     Note  the  odor  of  escaping  gases. 

Test  for  oxygen  by  inserting  a  glowing  splinter  into  the  tube. 

Test  for  combustible  gases  by  occasionally  applying  flame 
to  the  open  end  of  the  tube. 

Bring  to  the  mouth  of  the  tube  a  clear  drop  of  Ba(0H)2 
solution.     If  the  drop  becomes  turbid,  CO2  is  indicated. 


Observed  Phenomena. 

Steam  condenses  in  cold  part  of  tube. 
Oxygen  is  evolved. 


Carbon  Dioxid  is  evolved. 


A  Combustible  Gas  is  formed: 

(o)  Burning  with  a  luminous  flame,  black 
residue  remains  in  tube. 

(b)  Burning  with  a  blue  flame. 

(c)  Burning  as  in  (b)  and  with  odor  of  SO2. 
A  Sublimate  forms  in  the  cooler  part  of  the 

tube.     Examine  under  microscope. 


Indications. 

See  under  A. 

A  peroxid,  chlorate,  some 
oxids  (as  HgO),  alkali  ni- 
trates. 

Carbonates,  oxalates  (at 
high  temperature),  or- 
ganic matter. 

Hydrocarbons  from  organic 

matter. 
CO  from  oxalates. 
H2S  from  moist  sulphids.    . 


lOO     SALTS  OF   THE  METALS   AND  QUALITATIVE  ANALYSIS 


Observed  Phenomena. 

Colorless  with  partial  decomposition. 

Color  is  white  with  production  of  garlic  odor, 
crystalline. 

Color  is  white  when  cold.  Yellow  when  hot, 
crystalline. 

Color  is  white  —  it  sublimes  directly  with- 
out melting  and  blackens  with  NH4OH. 

A  white  sublimate  which  by  treatment  with 
slaked  lime  yields  NH3. 

A  white  sublimate  of  AS2O3  with  black 
residue  in  tube  and  odor  of  acetic  acid. 

Sublimate  is  gray,  consisting  of  small  glob- 
ules which  can  be  made  to  unite  by  rub- 
bing'. 

Sublimate  consists  of  reddish  yellow  to  red 
globules,  yellow  when  cold. 

Sublimate  darker  than  above  and  reddish 
yellow  when  cold. 

Sublimate  is  brown  to  black  "  metallic  mir- 
ror," soluble  in  NaClO. 

Ditto;  dead  black,  insoluble  in  NaClO. 

Sublimate  is  black  accompanied  by  violet 
vapor. 

Sublimate  black,  turning  red  when  rubbed. 
No    sublimate    is    formed,    but    the    color 

CHANGES  to 

Yellow  when  hot,  white  when  cold. 
Reddish  brown  when  hot,  yellow  when  cold. 
Black  when  hot,  red  when  cold. 
Black  when  hot,  brick-red  when  cold. 
Dark  orange  when  hot,  yellow  when  cold. 
Black  residue  without  other  visible  mani- 
festation. 
Substance  melts  without  a  sublimate  being 
formed. 


Indications, 

Oxalic  acid.    Plate  i,  Fig.  i. 
AS2O3.     Plate  I,  Fig.  2. 

HgCla.     Plate  i,  Fig.  3. 

HgCl. 

Ammonium  salts.     Plate  i, 

Fig.  4. 
Paris  green. 

Hg   from    HgO,    amalgam, 
etc.     Plate  I,  Fig.  5. 

Sulphur. 

Native  sulphid  of  arsenic. 

Metallic  arsenic. 

Metallic  antimony, 
lodin.     Plate  i,  Fig.  6. 

HgS,  cinnabar. 


ZnO. 

PbO  or  BiaOa.     (See  D.) 

HgO  (Hg  sublimes). 

FeaOa. 

Chromates  of  Pb,  etc. 

Oxids  of  Cu,  Co,  etc.     (See 

A.) 
Salts  of  the  alkaline  metals. 


C.   Flame  Test  with  Platinum  Wire. 


Introduce  the  substance  on  platinum  wire  into  the  edge 
of  the  flame.  More  satisfactory  results  are  sometimes  obtained 
if  the  solid  is  first  moistened  with  HCl  (page  yi,  note).  The 
flame  is  colored  as  follows:  by  Na,  yellow;  K,  violet;  Li,  carmine; 
Sr,  crimson;  Ca,  orange-red;  Ba,  yellowish  green;  Cu,  usually 
bright  green;  CUCI2,  an  intense  blue;  H3BO3,  pale  green;  Sb, 
greenish  blue;  Pb,  As,  Bi,  livid  blue. 


PLATE  I.  — SUBLIMATES. 


Fig.  I. 
Oxalic  Acid  (Sublimed). 


Fig.  3. 
Mercuric  Chlorid  (Sublimed). 


Fig.  2. 
Arsenic  Trioxid. 


Fig.  4. 
Ammonium  Sulphate  (Sublimed). 


Fig.  5. 
Mercury  from  HgO. 


ANALYSIS  IN   THE  DRY  WAY 


lOI 


D.  Blowpipe  Test  on  Plaster.* 

Smooth  plaster  slabs  about  i  inch  wide  and  4  inches  long  are 
well  suited  for  these  tests.  These  may  be  prepared  by  making 
a  magma  of  calcined  plaster  and  pouring  upon  a  glass  plate. 
Before  it  hardens  mark  deeply  with  a  spatula  into  slabs  of 
desired  shape  and,  after  it  is  thoroughly  dried,  break  as  marked. 

Make  a  little  depression  near  one  end  of  the  slab  and  in  it 
place  a  small  amount  of  the  substance  to  be  tested;  then  if 
a  fine  oxidizing  flame  is  made  to  play  over  the  surface  of  the 
assay,  characteristic  coatings  of  oxid  or  sublimate  may  be 
obtained. 

In  many  cases  the  character  of  the  substance  may  be  deter- 
mined more  easily  by  first  moistening  the  assay  with  various 
reagents.  Tetrachlorid  of  tin,  cobalt  nitrate,  and  "sulphur 
iodid"  are  the  most  valuable  of  the  reagents  so  used.  The 
"sulphur  iodid"  is  not  of  definite  composition,  but  a  mixture 
of  about  equal  weights  of  sulphur  and  potassium  iodid. 


D.   I.   Examination  without  Reagents. 
Observed  Phenomena.  Indications. 


Substance  melts  to  bright  metallic  globules 
with  brownish-yellow  deposit  near  assay. 
Requires  high  heat.     Assay  revolves. 

Substance  melts  to  bright  globule  with  coat- 
ing on  plaster,  deep  orange  when  hot,  light 
yellow  when  cold. 

Substance  remains  or  becomes  black  without 
melting.     No  coating  on  plaster. 

Substance  volatilizes  with  white  fumes,  but 
leaves  dark  stain;  gray  to  black. 

Substance  melts  with  white  or  gray  oxid  on 
assay. 

Porms  a  white  or  gray  oxid  without  fusion. 
Coating  on  plaster  is  yellow  over  brownish 
black. 


Silver. 


Lead  or  bismuth  (See  D.  II.) 


Copper    cr    iron.     (See    A; 

also  F.) 
Antimony  or  arsenic.     See 

F.) 
Tin.     (See  D.  III.) 

Cadmium. 


*  Substances  sufficiently  identified  by  previous  tests  have  been  omitted.  This 
method  will  be  found  useful  mainly  in  the  identification  of  metals. 

The  Author  was  greatly  aided  in  the  preparation  of  this  list  by  Mr.  Geo.  F.  S. 
Pearce  of  the  Harvard  Dental  School,  who  carefully  verified  each  test. 


102     SALTS  OF   THE  METALS   AND  QUALITATIVE  ANALYSIS 


Observed  Phenomena. 

Forms  bulky  white  oxid  with  active  combus- 
tion of  assay. 
Forms  gray  coating  easily  volatilized. 

Cherry-red  —  crimson  to  black  according  to 
amount  of  substance  deposited.  Odor  of 
rotten  horse-radish;  coating  not  permanent. 

White  coating  or  white  fumes  at  very  high 
heat.     Assay  burns  with  bluish-white  light. 

Silver-white.     Assay  remains  unchanged. 


Indications. 

Magnesium. 

Mercury  from  amalgams. 

(See  D.  II.) 
Selenium. 

Zinc.     (See  D.  III.) 
Platinum,  metallic. 


D.   II.   Cover  Substance  with  KI  and  S.     Use  Oxidizing  Flame. 


Observed  Phenomena. 

Dirty-white  and  light-gray  coating.  Treated 
with  fumes  of  strong  NH3  and  again  placed 
in  oxidizing  flame  gives  bright-red  color. 
Metallic  globule  is  dull  and  brittle. 

Dirty  white  half  an  inch  from  assay.  Brown 
directly  under  assay.  No  change  when 
treated  as  above  with  strong  ammonia 
fumes.  Metallic  globule  is  bright  and 
malleable. 

No  coating  near  assay.  Lead-colored,  one  to 
one  and  a  half  inches,  shading  to  yellow. 

Coating  bright  red  when  hot,  fading  to  yellow 
when  cold. 

Fine  brown  coating,  very  volatile. 


Indications. 


Bismuth. 
Lead. 

Mercury. 

Cadmium. 

Antimony. 


D.   III.   Examination  with  Solution  of  Cobalt  Nitrate. 

Heat  substance  on  plaster  in  the  oxidizing  flame,  moisten 
well  with  cobalt  nitrate,  and  again  apply  oxidizing  flame. 


Observed  Phenomena. 

Color  is  deep  blue. 

Substance  is  infusible. 

Color  is  fine  blue.     Substance  fusible. 

Color  is  yellowish  green. 
Drab  to  bluish  green. 


Indications. 

Aluminium. 

Infusible  silicates.    (SeeF.) 

Alkaline  silicate,  borate,  or 

phosphate. 
Zinc. 
Tin. 


ANALYSIS  IN   THE  DRY   WAY 


103 


D.   IV.   Examination  with  Tetrachlorid  of  Tin. 


Observed  Phenomena'. 

Coating  pale  blue  to  lavender. 
Coating  fine  blue,  in  places  almost  black. 
Delicate  pink  to  red  produced  only  by  oxidiz- 
ing flame. 


Indications. 

Bismuth. 

Antimony. 

Neutral  and  acid  chromates . 


E.   Bead  Tests. 

The  bead  tests  are  made  with  borax,  as  described  on  page  51, 
or  in  a  similar  manner  with  microscosmic  salt,  NaNH4HP04, 
which  by  action  of  the  heat  gives  up  NH3  and  H2O,  becoming 
sodium  metaphosphate,  NaPOs.  These  substances  fused  on  a 
loop  of  platinum  wire  unite  with  many  of  the  metallic  oxids, 
forming  "beads"  of  various  characteristic  colors,  some  of  the 
more  important  being  given  below. 

With  Borax. 

Co  in  the  oxidizing  flame  gives  an  intense  blue  bead. 

Ni  gives  a  red-brown,  yellow  when  cold. 

Cu  gives  a  green,  blue,  or  bluish  green  when  cold. 

Cr  gives  green. 

Fe  gives  a  red,  yellowish  when  cold. 

Mn  gives  an  amethyst. 


With  Microcosmic  Salt. 

Cobalt,  copper,  nickel,  and  iron  give  colors  similar  to  those 
obtained  with  borax.  Manganese  gives  a  violet  bead  when 
heated  in  the  oxidizing  flame,  but  a  colorless  one  in  the  reducing 
flame. 

F.   Special  Tests  Distinctive  or  Confirmatory. 

The  oxids  of  copper  and  iron  may  be  distinguished  by 
adding  a   drop  of  HNO3,  warming  gently  to  drive  off  excess 


I04     SALTS  OF   THE  METALS  AND  QUALITATIVE  ANALYSIS 

of  acid  (high  heat  will  decompose  the  nitrate,  giving  the  oxid 
again),  and  then  adding  a  drop  of  solution  of  K4FeCy6.  Fe 
will  give  a  dark-blue  coloration;   Cu  will  give  a  brown. 

To  distinguish  between  As  and  Sb  stains,  add  a  drop  of 
h3Apochlorite  solution  (NaClO).  The  arsenic  stain  will  dis- 
solve;  the  antimony  stain  will  remain  unaffected  (see  page  33). 

Antimony  gives  a  very  characteristic  coating  on  plaster  if 
treated  with  tetrachlorid  of  tin.  The  coating  is  bluish  black 
near  assay,  fading  away  to  a  very  delicate  color  at  greater 
distance.     It  appears  almost  immediately  and  is  permanent. 

In  case  of  suspected  siHcates  make  the  "siUca  skeleton"  with 
a  bead  of  microcosmic  salt  (page  92). 

Laboratory  Exercise  XXVI. 
Preliminary  tests  with  metals  and  solids  other  than  salts. 

Laboratory  Exercises  XXVII  and  XXVIII. 

Identification  of  unknown  metals  and  analysis  of  solid  sub- 
stances. 


PART    II. 

DENTAL   METALLURGY. 

INCLUDING  THE  CHEMISTRY  OF  ALLOYS,  AMALGAMS, 
SOLDERS,   AND   CEMENTS. 

CHAPTER  XL 
THE   METALS. 

Properties  of  the  Metals. 

Metals  are  malleable  in  order  as  follows  from  gold,  the  most 
malleable,  to  nickel,  the  least:  Au,  Ag,  Al,  Sn,  Cu,  Pt,  Pb,  Cd, 
Zn,  Fe,  Ni. 

Metals  are  ductile  from  most  to  least  as  follows:  Au,  Ag,  Pt, 
Fe,  Ni,  Cu,  Cd,  Al,  Zn,  Sn,  Pb. 

Metals  conduct  heat  and  electricity  in  the  same  order  until 
Sn  is  reached.  From  Sn  the  order  given  is  correct  for  heat 
but  not  for  electricity:  Ag,  Cu,  Au,  Al,  Zn,  Cd,  Sn,  Fe,  Pb, 
Pt,  Bi. 

The  melting-point  of  the  various  metals  is  of  considerable 
importance  in  the  preparation  of  alloys.  The  following  table 
has  been  compiled  from  the  latest  available  results.  The  de- 
grees given  are  according  tb  the  centigrade  scale: 

^t 2000°  Cu 1054°  Zn 420°  (bums) 

^i 1450°  Ag 954°  Pb 326° 

Cast  steel 1375°  Al 700°  Cd 320° 

Cast  iron 1275°  Mg 500°  (burns)   Bi 268° 

Au 1075°  Sb 432°  Sn 238° 


io6 


DENTAL  METALLURGY 


The  expansion  of  the  various  metals  under  the  influence  of 
heat  is  fairly  constant  and  there  have  been  determined  co- 
efficients of  expansion.  These  represent  the  amount  of  linear 
expansion  of  the  metals  due  to  a  rise  in  temperature  of  i°  C, 
usually  from  o°  to  i°.  The  coefflcients  are  not  absolutely  con- 
stant, and  the  amount  of  expansion  observed  between  o°  and  i° 
may  differ  somewhat  from  that  between  50°  and  51°.  The 
coefhcients  vary  widely  for  the  different  metals;  for  instance, 
in  passing  from  0°  to  100°  mercury  expands  1/16  of  its  linear 
measure,  copper  1/598,  and  platinum  1/1123. 

Hall's  Dental  Chemistry  gives  the  following  table  of  expan- 
sion from  cadmium  to  platinum: 


Cd. 
Pb. 
Zn. 
Al. 
Sn. 


1/326 
1/342 
1/343 
1/432 
1/448 


Cu. 
Bi. 

Au. 


1/518  Ni 1/787 

1/598  Fe  (cast) 1/934 

1/617  Sb 1/952 

1/689  Pt 1/1123 


The  only  other  general  property  of  the  metals  directly 
affecting  their  use  in  dental  practice  is  the  electric  or  galvanic, 
that  is,  the  electropositive  or  negative  relations  they  sustain  to 
one  another. 

The  metals  are   electropositive   to   each  other  in  the  fol- 
lowing order  from  zinc,  the  most  positive,  to  platinum,  the  least: 
Zn,  Cd,  Sn,  Pb,  Fe,  Ni,  Bi,  Sb,  Cu,  Ag,  Au,  Pt; 
and  C  is  negative  to  all. 

Thus  if  a  battery  is  constructed  with  Zn  as 
represented  in  the  cut  (Fig.  5),  and  iron  in  place 
of  the  carbon,  then  the  iron  will  be  electroneg- 
ative to  the  zinc,  and  hydrogen  will  be  evolved 
from  its  surface;  if,  on  the  other  hand,  Fe  is  used 
in  place  of  the  zinc,  and  the  carbon  remains  as  in 
the  cut,  the  Fe  will  be  electropositive  to  the 
carbon,  and  oxygen  will  be  evolved  from  its 
This  property  of  metals  has  a  direct  bearing  upon 


THE  METALS  107 

dental  science,  because  human  saliva  may  be  an  exciting  fluid 
for  the  generation  of  galvanic  currents,  its  activity  being  in- 
creased by  an  abnormal  reaction  either  acid  or  strongly  alkaline, 
and  it  is  only  necessary  to  place  in  the  mouth  properly  related 
metals,  as  amalgam  filKngs  or  otherwise,  to  produce  the  elements 
of  a  galvanic  battery. 

The  currents  thus  generated  are,  of  course,  infinitesimal,  but 
they  are  constant  and  may  aid  in  the  disintegration  of  fillings 
and  in  the  solution  of  the  constituent  metals.  Regarding  the 
extent  to  which  electric  currents  may  exist  in  the  mouth,  see 
Miller's  Micro-organisms  of  the  Human  Mouth. 


CHAPTER  XII. 

ALLOYS. 

An  intimate  union  of  two  or  more  metals,  usually  produced 
by  fusion,  forms  an  alloy.  Such  a  union  of  one  or  more  metals 
with  mercury  is  an  amalgam. 

An  alloy  designed  to  be  used  in  the  preparation  of  dental 
amalgams  is  known  as  an  amalgam  alloy. 

Some  metals  can  be  fused  together  in  all  proportions,  as 
Pb  and  Ag.  Others  can  be  made  to  unite  only  in  limited  pro- 
portions, as  Pb  and  Zn.  Lead  will  carry  only  i.6%  of  zinc, 
while  zinc  will  unite  with  only  1.2%  of  Pb.  Excess  in  either 
case  separates  out. 

The  properties  of  an  alloy  are,  as  a  rule,  the  modified  proper- 
ties of  its  constituent  metals.  An  exception  to  this  rule  might 
be  made  of  the  sonorous  quality  of  bell-metal  and  like  alloys, 
this  being  hardly  a  property  of  the  constituent  metals  at  all. 

Following  are  some  of  the  more  common  alloys.  The  pro- 
portions given  are  general  formulae  and  may,  as  a  rule,  be  varied 
considerably : 

Aluminium  bronze,  yellow,  resembles  gold,  Cu  92,  Al  8. 
Bell-metal,  Cu  80,  Sn  20. 
Brass,  Zn  i,  Cu  2. 
Britanniametal,  Cu  2,  Sn  82,  Sb  16. 

Bronze,  Cu  65  to  84,  Zn  from  31.5  to  11,  Sn  from  2.5  to  4. 
Coin  silver,  Ag  90,  Cu  10. 
Dental  alloys,  see  page  117. 
Dental  gold,  Cu  85,  Zn  15. 
German  silver,  Cu  50,  Ni  30,  Zn  20. 

108 


ALLOYS  109 

Composition  of  different  samples  of  German  silver  may  differ 
widely;  some  contain  about  2.5%  of  iron  and  the  amount  of 
Cu  may  vary  from  40  to  60%. 

Gun  metal,  Sn  11,  Cu  100. 

Solder,   see  page  127. 

Sterling  silver  must  contain  92.5%  Ag. 

Type  metal,   Pb  78,  Sb  15,  Bi  7. 

All  alloys  (excluding  amalgams)  are  solid  at  ordinary  tem- 
peratures with  one  exception;  this  one  is  an  alloy  of  one  part 
potassium  with  three  parts  sodium. 

The  melting-point  of  an  alloy  is  often  lower  than  that  of  the 
metals  entering  into  its  composition  and  usually  lower  than 
the  mean  melting-point  of  its  constituents. 

In  making  alloys  the  tendency  to  separation  of  the  several 
metals  is  greater  if  the  alloy  is  allowed  to  cool  slowly;  hence 
three  essentials  in  the  process  are:  Complete  fusion,  which 
makes  possible  thorough  mixing,  and  after  this  has  been  attained 
rapid  cooling.  As  the  fused  mass  is  to  be  cooled  as  quickly 
as  possible  after  fusion  is  complete,  it  is  desirable  to  use  the 
least  amount  of  heat  practicable  in  effecting  the  desired  result. 
To  this  end  fuse  first  the  metal  with  the  lowest  melting-point, 
then  add  other  metals  in  the  order  of  their  melting-points. 
The  more  difficultly  fusible  metal  will  in  a  sense  dissolve  in 
the  more  easily  fusible  metal;  an  alloy  is  formed  and  its  tem- 
perature has  been  kept  far  below  the  melting-point  of  the  high 
fusing  constituent.  This  general  rule,  however,  may  be  modified 
by  the  proportion  of  metal  used;  thus,  in  making  a  silver- tin 
amalgam-alloy  containing  60%  of  silver  it  is  better  first  to  melt 
the  silver  under  a  flux  of  carbonate  of  sodium  or  borax  to  prevent 
superficial  oxidation,  then  add  the  tin,  and  lastly  any  other 
metal  to  be  used.  The  mixing  is  attained  by  stirring  with  a 
wooden  stick  and  the  cooling  by  turning  quickly  into  a  cold  clean 
mold.  For  class  work  or  in  making  small  amounts  (20  grams) 
of  alloy,  the  Fletcher  melting  arrangement  shown  in  Fig.  6  is 


no  DENTAL  METALLURGY 

very  convenient.  The  metals  are  melted  in  the  graphite  crucible 
and  then  by  tipping  up  the  whole  contrivance  the  melted  metals 
flow  back  into  the  ingot  mold.  If  the  alloy  is  to  be  used  in  the 
preparation  of  dental  amalgams  it  must  be  reduced 
to  fine  turnings  or  filings  suitable  for  ready  amal- 
gamation. This  is  best  accomplished  in  the  lab- 
oratory by  means  of  a  coarse  file,  the  ingot  being 
held  by  a  vise.  The  fine  particles  of  iron  must 
next  be  carefully  removed  with  a  magnet,  and  then 
^^'  '  the  filings  may  be  annealed  if  desired. 
The  annealing  of  the  amalgam-alloys  may  be  accomplished 
by  placing  the  freshly  cut  sample  in  a  dry  test-tube  and  keeping 
the  test-tube  in  boiling  water  for  ten  or  twelve  minutes.  It  has 
been  claimed  that  this  process  is  one  of  superficial  oxidation  and 
the  changes  produced  seem  to  be  consistent  with  this  theory. 
Again,  it  is  claimed  that  the  change  is  a  molecular  one  of  some 
sort  due  to  change  of  temperature,  and  Prof.  G.  V.  Black  has 
shown  that  an  alloy  will  anneal  as  rapidly  in  an  atmosphere  of 
nitrogen  as  of  oxygen.  The  modification  of  properties  produced 
by  annealing  varies  somewhat  with  the  composition  of  the  alloy ; 
for  instance,  the  liabiHty  to  discoloration  is  less  in  the  annealed 
than  in  the  unannealed  sample,  if  the  alloy  contains  Ag  and  Sn, 
or  Ag,  Sn,  and  Zn,  but  if  Cu  is  a  constituent  the  reverse  condition 
has  been  found  to  exist. 

According  to  Professor  Hall  of  Northwestern  University, 
"annealed  alloys  take  up  less  mercury  than  unannealed  and  yield 
upon  mixing  a  greater  quantity  of  dirt,  which  consists  of  a  lower 
oxid  of  tin."  The  amalgam  made  from  an  annealed  alloy 
works  more  easily  than  from  an  unannealed. 

The  process  of  annealing  up  to  a  certain  point  seems  to  be, 
in  general,  beneficial;    but  beyond  this  point  it  may  be  detri- 
mental, the  amalgam  being  less  strong  and  more  liable  to  shrink. 
Professor  Black  has  shown  that  while  it  may  be  possible  to 
stop  the  process  of  annealing  at  such  a  point  that  a  given  alloy 


ALLOYS  III 

will  neither  shrink  nor  expand,  it  is  easy  to  carry  the  process 
too  far  and  the  farther  it  is  allowed  to  go  the  greater  the  shrink- 
age. It  is  probably  true  that  the  exact  effect  of  annealing 
will  vary  with  the  composition  of  the  alloy,  and  with  different 
proportions  of  metals  in  alloys  of  the  same  general  composition. 

Annealing  or   Gold. 

When  gold-foil  is  heated  to  redness  it  recovers  the  cohesive 
property  which  has  been  lost  largely  by  hammering.  It  is 
recommended  that  the  heating  be  done  in  an  electric  furnace 
or  on  plates  of  mica  or  platinum,  thus  insuring  uniformity  of 
effect  throughout  the  mass  which  it  is  practically  impossible 
to  obtain  by  holding  the  metal  in  the  flame.  See  Dental 
Cosmos,  Vol.  XL VII,  page  233. 

Non-cohesive  gold,  or  gold  in  which  the  cohesive  property 
cannot  be  developed  by  heating,  may  be  prepared  by  alloying 
or  treatment  with  carbon.  Corrugated  gold  is  of  this  variety 
and  is  prepared,  according  to  Essig,  by  carbonization  of  unsized 
paper  in  intimate  contact  with  the  metal.  See  Essig,  Dental 
Metallurgy,  page  173. 

In  anneaHng  platinum  a  high  degree  of  heat  is  required, 
but  the  heat  should  be  raised  gradually,  and  in  this  case  also 
the  electric  furnace  furnishes  an  ideal  method. 

Laboratory  Exercise  XXIX. 
Analysis  of  an  Unknown  Alloy. 


CHAPTER  XIII. 
AMALGAMS. 

In  general,  amalgams  may  be  made  in  three  different  ways: 
First,  by  direct  union  of  the  constituents,  as  in  the  manufacture 
of  sodium  amalgam  (page  113);  second,  by  electrolysis  of 
strong  solutions  of  metallic  salts  in  presence  of  mercury,  as 
in  copper  amalgam  (page  114),  and  third,  by  double  decom- 
position as  illustrated  in  the  preparation  of  ammonium  amal- 
gam (page  114). 

Amalgams  possess  the  pecuKar  property  of  ''setting"  or 
hardening  within  a  short  time  after  mixing.  This  in  some  cases 
seems  to  be  a  process  of  crystalUzation,  and  in  all  cases  is  prob- 
ably due  to  molecular  rearrangement  of  some  sort. 

After  an  amalgam  has  ''set"  to  a  sufficient  extent  to  make 
it  hard  to  work  it  may  be  softened  by  application  of  gentle 
heat.  Continued  reheating  is  detrimental  to  the  quaHty  of  the 
amalgam,  and  should  be  avoided;  this  is  particularly  true  of 
copper  amalgam.  It  is  also  possible  to  sometimes  restore  the 
plastic  quality  of  an  amalgam  by  adding  a  further  shght  amount 
of  mercury,  but  the  union  of  the  second  lot  of  Hg  after  the 
first  has  partly  hardened  is  very  unsatisfactory  and  results  in  a 
weakened  product. 

Flow  of  Amalgams.  —  This  property  may  be  defined  as  the 
tendency  to  flatten  or  change  shape  under  stress  or  pressure. 
It  is  common  to  most  amalgams  (copper  amalgam  being  an 
exception,  according  to  Dr.  Black),  and  is  possessed  by  many 
alloys  other  than  amalgams. 

Tests  for  "flow"  may  be  made  with  the  "dynamometer"  on 
cubes  of  alloy  or  amalgam  measuring  one-tenth  of  an  inch  each 
way  and  the  results  expressed  in  percentage  of  increase  or  de- 


AMALGAMS 


113 


crease  of  one  dimension.  The  dynamometer  used  for  this  pur- 
pose is  pictured  in  Fig.  7  and  is  a  modification  of  the  apparatus 
devised  by  Dr.  Black  and  described  on  pages  408  and  409  of  the 
Dental  Cosmos,  Vol.  37,  A- A  being  the  molds  in  which  the 
cubes  of  amalgams  are  set  and  B  the  point  in  the  apparatus 
where  the  cube  after  setting  is  introduced  with  a  pair  of  fine 
forceps.  The  dial  is  supplied  with  two  hands,  one  which  flies 
back  the  instant  the  cube  breaks,  the  other  remaining  to  indicate 
the  number  of  pounds  applied  necessary  to  crush  the  cube. 
The  cubes  of  i/io  inch  are  best  suited  for  students'  practice, 


Fig.  7. 

with  a  dial  constructed  to  record  250  pounds  pressure.  For 
accurate  comparisons  of  thoroughly  made  amalgams  the  cubes 
must  be  made  smaller. 

Binary  amalgams,  as  they  are  sometimes  called,  are  those 
consisting  of  only  one  metal  besides  mercury.  These  are  rarely 
used  in  dental  practice,  but  from  them  the  properties  of  the 
amalgamated  metal  are  most  easily  observed. 

Sodium  amalgam  may  be  made  by  direct  union  of  the 
constituent  elements.  The  mercury  should  be  placed  in  an 
open  dish  under  a  hood,  and  the  sodium  added  in  small  well- 
cleaned  pieces. 


114  DENTAL  METALLURGY 

The  union  is  accompanied  by  a  slight  hissing  noise,  an  eleva- 
tion of  temperature  and  evolution  of  vapor  carrying  more  or 
less  mercury,  hence  dangerous  to  breathe.  An  amalgam  con- 
taining 1%  sodium  is  a  viscid  liquid;  if  it  contains  5%  sodium 
it  is  a  hard  solid  and  intermediate  percentages  give  varying 
degrees  of  firmness.  Sodium  amalgam,  if  made  with  arsenic-free 
Hg,  is  a  very  convenient  reagent  to  use  in  making  Fleitmann's 
Test  (page  29). 

Ammonium  amalgam  has  no  use  in  dentistry,  but  it  is  of 
interest  in  that  it  is  the  nearest  approach  to  which  we  may 
attain  to  the  isolation  of  the  purely  hypothetical  metal  ammo- 
nium. It  is  easily  made  by  adding  sodium  amalgam  to  a  cold 
saturated  solution  of  ammonium  chlorid,  thus  illustrating  the 
third  general  method  of  preparation  of  amalgams.  It  rapidly 
decomposes  at  ordinary  temperature  with  the  liberation  of  free 
hydrogen,  ammonia-gas,  and  metalHc  mercury.  The  H  thus 
liberated  exhibits  the  properties  of  nascent  H,  indicating  that  in 
the  amalgam  it  existed  in  true  chemical  combination,  that  is 
NH4,  rather  than  in  any  physical  solution.  At  ordinary  tem- 
perature ammonium  amalgam  is  a  soft,  pasty,  very  porous 
mass,  but  at  much  reduced  temperature  it  becomes  soHd  and 
crystalKne,  although  at  —39°  (the  freezing-point  of  Hg)  H  and 
NH3  are  still  given  off. 

Copper  amalgam  is  by  far  the  most  valuable  of  this  class 
of  amalgams.  It  may  be  made  by  amalgamating  precipitated 
copper  after  moistening  it  with  nitrate  of  mercury  (Essig). 
The  precipitated  Cu  may  be  prepared  by  action  of  metalhc  Zn 
in  a  slightly  acid  copper  sulphate  solution,  but  must  be  thor- 
oughly washed  with  hot  water  to  free  it  from  zinc  chlorid.  The 
amalgamation  may  be  effected  by  use  of  mortar  and  pestle. 
Rollins'  method*  by  electrolysis  of  strong  copper  sulphate  solu- 

*  Details  of  this  method  may  be  found  in  the  Boston  Medical  and  Surgical 
Journal,  February,  1886;  also  in  Mitchell's  Dental  Chemistry.    ■ 


AMALGAMS  1 15 

tion  is  rather  unwieldly,  but  illustrates  very  well  the  second 
general  process  for  the  manufacture  of  amalgams. 

Copper  amalgam,  according  to  Black,  is  absolutely  rigid 
after  it  has  once  set  and  does  not  flow  even  to  a  slight  extent. 
It  is  fine-grained  and  very  hard.  It  is  reduced  in  strength  by 
reheating  and  does  not  expand  or  contract.  In  the  mouth  copper 
amalgam  dissolves  with  comparative  rapidity  owing  to  the 
ready  formation  first  of  copper  sulphid,  then,  by  the  oxidation  of 
this  compound,  of  the  sulphate.  It  blackens  rapidly  and  in  con- 
sequence of  the  tendency  to  dissolve  just  mentioned,  it  may 
penetrate  the  dentine  and  thus  discolor  the  tooth  itself. 

Gold  amalgam  is  readily  made,  but  does  not,  by  itself,  harden 
well.  An  amalgam  containing  one  part  of  gold  to  six  of  mer- 
cury will  crystallize  in  four-sided  prisms  (Litch). 

Platinum  amalgam  is  very  smooth,  is  formed  with  diffi- 
culty unless  the  Pt  is  very  finely  divided,  and,  like  gold,  does  not 
harden  well. 

Silver  amalgam,  easily  made  but  tends  to  expand. 

Tin  amalgam,  alone  shrinks  badly. 

Zinc  amalgam,  readily  made,  is  white,  but  too  brittle  to 
be  of  service. 

Cadmium  amalgam  may  be  easily  made  at  ordinary  tem- 
perature, "sets  quickly,  and  resists  sufficiently,  but  fillings  con- 
taining it  gradually  soften  and  disintegrate  and  may  stain 
the  dentine  bright  yellow  by  formation  of  cadmium  sulphid." 
(Mitchell.) 

Effect  of  Various  Metals  in  Amalgam  Alloys. 

With  the  properties  of  these  simpler  combinations  before 
us  it  becomes  easy  to  understand  the  effect  the  addition  of  the 
various  metals  will  have  upon  the  properties  of  a  silver-tin 
alloy;  for  practically  all  amalgam  alloys  are  silver- tin  alloys, 
either  simple  or  combined  with  one  or  more  other  metals. 

Silver  and  tin  are  the  most  valuable  constituents  of  amalgam 


Ii6  DENTAL  METALLURGY 

alloys.  Silver  is  essential  to  the  proper  setting  and  hardening 
of  the  amalgam.  It  tends  to  increase  expansion  and  to  hasten 
setting,  while  tin  possesses  the  opposite  characteristics.  Com- 
bined with  tin  in  the  proportion  of  65%  silver  to  35%  tin,  it 
forms  an  amalgam  alloy  perhaps  more  largely  used  than  any 
other.  It  was  this  combination  that  Dr.  Black  succeeded  in 
''annealing  to  zero,"  that  is,  so  that  upon  testing  it  showed 
neither  expansion  nor  contraction. 

Pure  silver-tin  alloys  will  flow  from  2.5  to  10%. 

Authorities  seem  to  agree  that  if  a  Ag-Sn  alloy  contains 
75%  or  more  of  silver  it  will  expand  only;  while  an  alloy  con- 
taining from  50  to  61  or  62%  of  silver  will  shrink  only;  and 
one  containing  less  than  50%  of  silver  will  first  shrink  and  then 
expand. 

The  larger  the  proportion  of  tin  the  easier  will  the  alloy  cut,, 
but  the  coarser  will  be  the  filings. 

Zinc  added  to  a  silver-tin  alloy  tends  to  whiten  the  amalgam, 
hastens  setting,  increases  the  flow,  and,  according  to  Essig, 
"causes  a  great  but  slow  expansion." 

Cadmium,  see  above. 

Antimony  gives  a  fine  grain  alloy  and  when  the  Ag  is  less 
than  50%  is  supposed  to  control  shrinkage. 

Bismuth  will  increase  the  flow  of  the  amalgam;  it  is  some- 
times used  in  low-grade  Ag-Sn  alloys  to  control  shrinkage. 

Copper  tends  to  diminish  flow  and  gives  a  strength  under 
pressure,  sets  quickly,  gives  better  margins,  and  by  some  is 
believed  to  have  preservative  influence  on  the  tooth  substance, 
but  the  more  copper  in  an  alloy  the  more  rapidly  does  it  dis- 
color. 

Gold.  —  From  three  to  seven  per  cent  of  Au  in  a  silver-tin 
alloy  diminishes  shrinkage,  helps  the  color  and  adds  to  crush- 
ing strength.     The  fihng  from  such  an  alloy  will  be  very  fine. 

Dr.  Black  says  5%  of  gold  gives  a  softer  working  property 
but  retards  setting  of  the  amalgam,  and  makes  it  otherwise 


AMALGAMS 


117 


difficult  to  give  a  good  finish  to  the  filling  (Dental  Cosmos, 
Vol.  38,  page  988). 

Platinum,  according  to  Black,  is  not  a  desirable  addition 
to  a  silver-tin  alloy.  It  gives  an  alloy  furnishing  very  fine  filing, 
which  produces  a  dirty  working,  slow-setting  amalgam. 

Excess  of  Mercury.  —  In  the  preparation  of  an  amalgam 
from  a  dental  alloy  it  is  usual  to  add  more  mercury  than  the 
finished  product  requires  and  then  squeeze  out  the  excess  be- 
tween the  fingers  or  otherwise.  In  filling  a  cavity,  still  more 
mercury  is  forced  out,  so  that  the  composition  of  the  deeper 
portions  of  a  filling  varies  from  the  outer  portions  and  probably 
accounts  for  the  inequaHties  in  expansion  or  contraction.  The 
excess  of  Hg  from  the  surface  of  a  filHng  may  be  absorbed  by 
a  little  hot  gold  or  pure  tin  or  by  finely  divided  silver. 

Following  is  a  short  list  of  dental  alloys,  most  of  which  may 
be  easily  prepared : 


Arington's  (S.  S.  White's) 

*(C.  A.  S.)  alloy,  C.  Ash  Sons  Co. 

Chase  copper-amalgam  alloy 

Chase's  incisor  alloy 

^Fellowship  alloy 

Flagg's  submarine  alloy 

Fletcher's  gold  alloy  (old) 

High-grade  alloy  {7 Wo  gold) 

Harris's  amalgam  alloy 

King's  occidental  alloy 

*Odontographic  alloy 

*Standard  alloy 

Standard  dental  alloy  (Eckfeldt) . 

60%  silver  alloy 

Temporary  alloy 

*True  dentalloy 

*Twentieth  century 


Sn.     Ag.     Au.     Cu.     Zn.    Sb 


57-5 
27.16 

50 

40 

26.80 

35 

56 

4I-S 


75 


27.13 
27.13 


42.5 

•54 
50 
50 

67-45 
60 
40 

49 
40 

42.75 
66.87 

53-55 
52 
60 
10 

65-91 
67.03 


4 
7-5 


0.28 
8.82 
4-4 


5.02 
10 

5-73 
S 


4-9 


5-21 

4.87 


0.90 


0-55 


7 

2.5 
trace 


1-52 
1 .  10 


5 
10 


*  Analyses  by  Dr.  P.  J.  Bums  of  the  Mass.  Inst.  Technology,  reported  in  the 
Journal  of  the  AUied  Societies,  June,  1908. 

The  excess  of  mercury  which  has  to  be  squeezed  out  of  an 
amalgam  carries  with  it  more  or  less  of  the  constituent  metals. 


Il8  DENTAL  METALLURGY 

Hall  found  that  whatever  the  amount  of  mercury  expressed,  it 
carried  just  about  i%  of  tin.  In  the  author's  experience  this 
amount  has  reached  nearly  i|%  of  tin.  Silver  is  carried  out  to 
a  much  less  extent  than  tin,  so  it  is  not  impossible  to  carelessly 
make  an  amalgam  and  squeeze  out  enough  mercury  to  change 
the  proportion  of  Ag  and  Sn  in  the  alloy.  This  change  will,  of 
course,  be  very  slight,  but  we  have  seen  that  the  contraction  and 
expansion  of  amalgams  may  be  affected  by  slight  changes  in 
composition. 

These  formulas  have  been  selected  from  various  sources  with 
a  view  to  giving  the  student  opportunity  to  study  effects  ob- 
tained by  varying  percentages  of  Sn  and  Ag,  and  by  introduc- 
tion of  other  metals,  Cu,  Zn,  etc. 

Tests  for  Amalgams. 

Color  Test.  —  This  is  made  upon  a  freshly  amalgamated 
alloy,  rolled  into  about  the  shape  and  size  of  a  small  pea,  with 
a  view  to  determine  the  amount  of  discoloration  the  amalgam 
is  Hable  to  undergo  in  the  mouth. 

A  ball  of  amalgam  carefully  smoothed  on  at  least  one  side 
is  placed  for  forty-eight  hours  in  a  saturated  solution  of  hydro- 
gen sulphid,  and  after  that  time  its  color  is  compared  with  other 
amalgams  similarly  treated,  or  with  amalgam  of  a  similar  com- 
position which  has  not  been  treated. 

Test  for  Expansion  or  Contraction. 

Black  has  shown  that  tests  of  this  nature  to  be  of  any  value 
must  be  made  in  such  a  way  that  the  amount  of  change  in  the 
volume  can  be  measured,  and  that  the  simple  method  of  pack- 
ing glass  tubes  and  using  colored  ink  is  wholly  unreliable. 

The  author  uses  for  this  purpose  an  apparatus  similar  to 
one  described  by  Prof.  Vernon  J.  Hall.  The  amalgam  is  packed 
closely  into  a  "well"  in  a  steel  block,  then  the  block  is  placed 


AMALGAMS 


119 


in  the  apparatus  so  that  a  counterpoised  steel  plunger  rests  on 
the  column  of  amalgam.  This  plunger  is  operated  by  a  very 
long  needle  and  attached  at  a  point  so  near  the  pivotal  support 
of  the  needle  that  a  rise  or  fall  of  the  plunger  of  1/2500  of  an 
inch  moves  the  tip  of  the  needle,  at  the  scale,  1/16  of  an  inch, 
or  one  degree.  If  the  needle  rises  half  a  degree,  which  may 
easily  be  read,  it  would  indicate  an  expansion  of  the  amalgam 
of  1/5000  of  an  inch. 

There  are  two  wells  in  each  block  and  both  of  exactly  the 
same  depth.  The  figure  given  below  will  make  this  explanation 
easily  understood,  A  being  the  steel  block  carrying  the  amalgam. 


Fig.  8. 


Test  for  Crushing  Strength  and  Flow.  —  The  test  is  made 
with  Dr.  Black's  dynamometer  (page  113)  upon  cubical  blocks 
of  amalgam  which  have  been  allowed  to  "set"  for  at  least  two 
days,  and  which  measure  i/io  of  an  inch  each  way. 

Specific  gravity  may  be  obtained  by  weighing  the  sample 
first  in  water,  then  in  air,  and  dividing  the  weight  in  air  by 
the  difference  between  the  two  weights  obtained. 

It  is  instructive  to  make  these  tests  on  amalgam  from  alloys 
of  varying  composition,  also  on  annealed  and  unannealed  alloys 
of  the  same  composition. 


CHAPTER  XIV. 
DENTAL  CEMENTS. 

Dental  cements,  largely  used  as  temporary  fillings  and  Knings 
of  cavities,  contain  oxid  of  zinc,  oxid  of  copper,  or  rarely  sulphate 
of  zinc,  combined,  at  the  time  the  cement  is  used,  with  phosphoric 
acid  or  with  a  solution  of  zinc  chlorid. 

There  are  six  forms  of  dental  cements  which  might  be  men- 
tioned: the  oxyphosphate  of  zinc,  oxyphosphate  of  copper,  arti- 
ficial enamel,  oxychlorid  of  zinc,  oxysulphate  of  zinc,  and  tin 
cement.     Of  these  the  last  three  are  but  little  used. 

Oxyphosphate  .of  Zinc.  —  This  is  the  most  serviceable  of 
the  preparations  of  this  class  unless  exception  is  made  of  the  new 
artificial  enamels,  which  have  not  been  in  use  long  enough  to 
warrant  positive  assertions  as  to  their  comparative  value. 

The  oxyphosphate  cement  is  usually  made  by  adding  a 
powder,  consisting  largely  of  pure  oxid  of  zinc,  colored  by  a 
sHght  amount  of  other  metallic  oxids,  to  a  liquid  consisting  of 
deliquesced  phosphoric  acid  (or  a  solution  of  phosphoric  acid 
in  which  zinc  phosphate,  and  possibly  slight  amounts  of  other 
phosphates,  have  been  dissolved),  till  a  putty-like  mass  results, 
which  rapidly  hardens  and  becomes  capable  of  receiving  a  con- 
siderable polish.  When  the  phosphoric  acid  used  is  the  glacial 
acid,  the  cement  may  be  spoken  of  as  a  metaphosphate,  because 
the  glacial  acid,  before  the  addition  of  water,  and  to  a  certain 
extent  afterwards,  is  actually  metaphosphoric  acid,  HPO3.  The 
metaphosphoric  acid  by  boiling  with  water  or  gradually  by  addi- 
tion of  water  without  boiling  becomes  the  orthophosphoric  acid 
(H3PO4). 

Hall's    Dental    Chemistry  takes    the   following    tests   from 


DENTAL  CEMENTS  121 

Flagg's  Plastics  and  Plastic  Filling,  as  characterizing  a  good 
ox5q)hospliate  cement. 

General  Tests,  i .  When  first  mixed  it  should  yield  a  tough 
mass  which  when  removed  from  the  spatula  does  not  adhere 
to  the  fingers  and  can  be  rolled  into  a  pliable  pellet. 

2.  It  should  have  a  glassy  surface;  and,  at  the  end  of  two 
or  three  minutes,  it  should  rebound  when  dropped  upon  wood, 
glass,  or  porcelain. 

3.  At  the  end  of  five  minutes  it  should  be  quite  hard  and 
should  sound  like  porcelain  when  tapped. 

4.  After  ten  or  fifteen  minutes  it  should  be  dented  with 
difficulty,  and  when  broken  should  show  a  clean,  sharp  fracture. 

5.  After  twenty  minutes  it  should  be  very  hard,  and  should 
be  capable  of  taking  a  good  burnish. 

6.  In  thirty  minutes  it  should  have  little  or  no  acid  taste. 

Arsenic  is  a  frequent  impurity  in  both  zinc  oxid  and  phos- 
phoric acid,  and  if  present  is  very  liable  to  produce  an  irritating 
cement,  sometimes  causing  considerable  trouble;  hence,  the 
material  entering  into  the  composition  of  any  dental  cement 
should  be  free  from  arsenic  (see  pages  28  to  31  for  arsenic  tests). 

The  purer  the  zinc  oxid  and  the  phosphoric  acid,  from  which 
the  cement  is  made,  the  more  durable  it  is  found  to  be;  so,  aside 
from  any  question  of  irritation,  it  is  quite  necessary  for  the  sake 
of  the  cement  itself  that  the  ingredients  be  pure. 

It  is  not  intended  to  give  the  impression  that  the  liquid  should 
consist  only  of  glacial  phosphoric  acid  or  the  powder  only  of  oxid 
of  zinc.  A  cement  thus  made  would  set  so  rapidly  that  it  would 
be  of  no  practical  value.  The  resulting  mass  would  also  prob- 
ably be  crumbly.  The  powder  or  the  liquid,  one  or  the  other, 
is  usually  mixed  with  phosphates  of  the  heavy  metals  which 
would  be  insoluble  in  water,  but  which  would  dissolve  in  the 
strong  phosphoric  acid. 

A  pure  ZnO  may  be  made  by  calcining  the  precipitated 
carbonate  of  zinc,  Zus (OH) 6(003)2  +  heat  =  5  ZnO  +  2  CO2  + 


122  DENTAL   METALLURGY 

3  H2O.    The  heat  should  be  below  500°  F.,  because,  if  too  strongly 
heated,  the  color  suffers,  becoming  yellowish. 

Another  method  of  making  pure  oxid  of  zinc  is  given  as 
follows:  Dissolve  pure  zinc  in  nitric  acid,  evaporate  to  dryness, 
and  heat  till  fumes  cease  to  be  given  off.  The  mechanical  effect 
of  the  escaping  oxids  of  nitrogen  is  said  to  leave  the  ZnO  in  the 
form  of  a  very  fine  powder. 

A  pure  phosphoric  acid  can  be  made  from  the  ortho-acid 
by  heating  till  the  white  fumes  begin  to  come  off,  then  heating 
to  redness,  cooling  and  dissolving  in  H2O  to  a  thick  syrup.  In 
mixing  cements,  the  powder  should  be  worked  into  the  liquid 
till  the  desired  consistency  is  obtained. 

Oxyphosphate  cement  and  all  cements  having  zinc  oxid  for 
a  base  tend  to  dissolve  in  the  fluids  of  the  mouth,  lactic  acid  and 
ammonium  salts  being  particularly  good  solvents  for  this  class 
of  compounds.  The  addition  of  ferric  oxid  to  ox3Aphosphate 
cement  increases  resistance  to  disintegration.  One  part  of 
ferric  oxid  to  6  to  10  of  zinc  oxid  is  recommended  by  Rollins  in 
the  International  Dental  Journal. 

Oxychlorid  of  zinc  is  more  easily  soluble  than  ox;)^hos- 
phate.  It  shrinks  more,  but  is  credited  with  a  preservative 
action  on  dentine  and  hence  is  used  to  some  extent  as  a  lining. 

The  powder  of  the  oxychlorid  cement  is  ZnO  with  sometimes 
a  little  borax,  or  silica,  or  both,  added.  A  good  oxychlorid 
cement  will  set  in  fifteen  or  twenty  minutes,  but  keeps  on  grow- 
ing harder  for  several  hours.  The  following  formula  is  recom- 
mended. 

Formula  for  Oxychlorid  Cement. 

Oxid  of  zinc  10  grams,  borax  o.i  gram,  and  powdered  silica 
0.2  gram. 

Transfer  to  clay  crucible  and  calcine  for  one-half  hour  in 
furnace  at  bright-red  heat.  Pulverize,  sift,  and  bottle.  The 
liquid  to  be  used  with  this  powder  consists  of  10  c.c.  of  pure 
HCl  saturated  with  pure  zinc  and  filtered  through  glass  wool. 


DENTAL   CEMENTS  1 23 

Oxy sulphate  of  Zinc.  —  This  is  used  still  less  than  the  oxy- 
chlorid.  It  is  non-irritating,  dissolves  easily,  and  is  compara- 
tively soft.  The  following  formula  is  taken  from  Hall's  Dental 
Chemistry. 

Formula  for  Oxysulphate  Cement. 

Ten  grams  oxid  of  zinc,  4  grams  sulphate  of  zinc.  Dry,  mix, 
calcine  for  one-half  hour,  and  sift. 

Liquid  to  be  used  with  the  powder  may  be  made  by  dissolv- 
ing 2  grams  of  zinc  chlorid  in  10  c.c.  of  water.  This  gives  a 
turbid  solution  and  should  be  shaken  when  used. 

Oxyphosphate  of  copper  cement  (Ames's)  consists  of  the 
usual  powder  and  Hquid.  The  powder  contains  oxids  of  cop- 
per, iron  (slight  amount),  cobalt,  and  zinc,  and,  of  course,  is 
black  in  color.  The  liquid  is  phosphoric  acid  holding  in  solution 
a  certain  amount  of  phosphate  of  zinc. 

The  cement  resulting  from  this  combination  was  found  to 
be  hard,  showing  practically  no  change  of  volume  and  resisting 
the  solvent  action  of  the  saHva. 

Tin  Cement. 

Dr.  Arthur  Scheuer,  of  Tephtz,  Bohemia,  recommends  a 
preparation  composed  of  a  finely  pulverized  tin  sponge  and  zinc 
oxid  mixed  with  glacial  phosphoric  acid.  "  The  powder  is  of  a 
light-gray  color,  becoming  sHghtly  darker  when  mixed  with  the 
acid,  but  regains  its  original  color  after  setting.  A  tin-cement 
filling  can  be  easily  inserted  and  when  poHshed  it  has  a  metalHc 
appearance."     (Dental  Cosmos,  May,  1904.) 

Artificial  Enamel.  —  Several  preparations  have  been  put  on 
the  market  under  this  name,  in  each  case  with  the  claim  that  it 
makes  a  much  harder  cement  and  one  which  resists  disintegra- 
tion to  a  much  greater  extent  than  the  ordinary  zinc  preparations. 

The  specifications  of  a  German  patent,  under  which  one  of 
these  preparations  is  manufactured,  claim  that  the  powder  con- 


124  DENTAL  METALLURGY 

sists  of  a  mixture  of  the  oxids  of  beryllium  and  silicon,  together 
with  alumina  and  lime.  The  Hquid  consists  of  a  50%  solution 
of  orthophosphoric  acid  in  which  aluminium  phosphate  and  zinc 
phosphate  have  been  dissolved. 

When  mixed  in  the  usual  manner  these  produce  a  cement 
which  is  much  harder  and  less  soluble  than  any  of  the  prepara- 
tions previously  considered. 

An  advertisement  of  one  of  these  preparations  claims  that 
its  success  is  due  to  the  use  of  a  very  valuable  compound,  without 
which  it  would  be  worthless,  and,  so  far  as  the  author  has  had 
opportunity  to  investigate  this  subject,  this  statement  seems  to 
be  true.  A  qualitative  analysis  confirms  the  claim  of  the 
patent  specifications  both  in  regard  to  the  composition  of  the 
liquid  and  the  presence  of  oxid  of  beryllium  in  the  powder,  and 
it  is  probable  that  the  value  of  these  preparations  depends 
largely  upon  the  proportion  of  beryllium  entering  into  their 
composition. 

Beryllium  is  a  rare  metal  which  occurs  naturally  with  alumi- 
nium as  a  silicate.  It  forms  basic  compounds  of  such  character 
as  makes  it  suitable  for  use  in  dental  cement. 

The  cement  powders  may  be  tested  for  beryllium  as  fol- 
lows: Fuse  a  Httle  of  the  powder  with  sodium  carbonate  (or 
the  double  sodium  potassium  carbonate);  dissolve  the  fused 
mass  in  dilute  hydrochloric  acid;  evaporate  to  dryness  and 
heat  to  120°  C.  to  dehydrate  the  silica;  take  up  in  water  with  a 
little  HCl  and  filter;  to  the  filtrate  (probably  containing  Al, 
Be,  Zn,  and  Ca)  add  a  Httle  ammonium  chlorid,  and  an  excess 
of  ammonium  carbonate,  A1(0H)3,  Be(0H)2,  and  CaCOs,  will 
be  precipitated.  The  berylHum,  however,  is  easily  soluble  in 
the  excess  of  (NH4)2C03.  Warm  (not  boil)  and  allow  to  stand 
for  some  time  to  insure  complete  separation  of  Al.  (Note.  — 
A1(0H)3  is  much  less  soluble  in  solution  of  (NH4)2C03  than  in 
either  NH4OH  or  even  NH4OH  and  NH4CI.)  Filter.  Boil  the 
filtrate  for  a  long  time,  when  the  beryllium  and  some  zinc  will 


DENTAL   CEMENTS  125 

be  precipitated.  Filter  and  dissolve  precipitate  off  paper  in 
dilute  HCl.  To  the  filtrate  containing  BeCl2  and  ZnCl2  add 
NH4CI  in  excess  and  NH4OH,  which  will  give  a  precipitate  of 
Be(0H)2.  If  Be  and  Zn  only  are  present,  the  separation  by 
boiling  may  be  unnecessary. 

The  Hquid  may  be  tested  for  dissolved  phosphates  by  dilut- 
ing with  water  and  adding  ammonia  till  alkahne ;  if  the  mixture 
remains  clear,  phosphates  of  alumina,  calcium,  or  zinc  are 
absent.  Care  should  be  used,  however,  in  the  addition  of  the 
ammonia,  as  an  excess  of  this  reagent  will  redissolve  phosphate 
of  zinc. 

If  the  ammonia  is  too  strong,  a  precipitate  of  ammonium 
phosphate  may  be  obtained,  but  this  may  be  easily  re-dissolved 
by  the  simple  addition  of  water. 


CHAPTER   XV. 
FUSIBLE    METALS  AND    SOLDERS. 

Fusible  Metals. 

Under  the  head  of  fusible  alloys  properly  come  many  of 
the  alloys  considered  on  page  128  as  solders.  The  fusible  alloy 
usually  contains  lead  or  bismuth  together  with  tin  and  occa- 
sionally cadmium.  This  may  be  mixed  in  such  proportions  that 
the  melting-point  may  be  anything  desired  down  to  63°  C. 
These  alloys  are  largely  used  in  the  dental  laboratory.  Mellot's 
metal,  composed  of  bismuth  8  parts,  tin  5  parts  and  lead  3 
parts,  is  perhaps  the  most  serviceable.  This  melts  at  about 
the  temperature  of  boiling  water.  Wood's  metal,  melting  at 
about  65°  C,  is  composed  of  bismuth  4  parts,  tin  i,  lead  2,  and 
cadmium  i.  Rose's  metal  is  bismuth  2  parts,  tin  i,  and  lead  i. 
This  melts  at  about  95°  C. 

Babbitt  Metal,  much  used  in  the  manufacture  of  dies,  is 
composed  of  copper  i  part,  antimony  2,  and  tin  8.  The  for- 
mula of  common  Babbitt  metal  on  the  market  will  be  found  to 
differ  somewhat  from  the  above  and  is  not  so  well  suited  for 
dental  purposes. 

According  to  Essig's  Dental  Metallurgy,  Dr.  C.  M.  Rich- 
mond used  a  fusible  alloy  in  crown  and  bridge  work  which  he 
states  is  as  hard  as  zinc  and  can  be  melted  at  150°  F.  and 
poured  into  a  plaster  impression  without  generating  steam. 
The  formula  of  this  alloy  is  as  follows:  Tin  20  parts,  lead  19, 
cadmium  13,  and  bismuth  48.  The  following  fusible-metal 
alloys  are  also  suitable  for  the  purpose. 

Tin.                  Lead.               Bismuth.  Melting-point  of  Alloy. 

12                       2  236°  F.  or  113°  C. 

533  202°  F.  or    94°  C. 

3                     S                      8  197°  F.  or    92°  C. 

126 


FUSIBLE  METALS  AND  SOLDERS 


127 


The  fusing-point  of  an  alloy  may  be  determined  by  melt- 
ing under  a  liquid  of  sufficiently  high  boihng-point  and  then 
carefully  noting  the  temperature  at  which  the  melted  alloy 
soHdifies.  Care  must  be  taken  that 
the  temperature  of  the  alloy  is 
exactly  the  same  as  recorded  by 
the  thermometer.  To  insure  this, 
in  the  case  of  an  alloy  with  low 
melting-point,  it  is  usually  suffi- 
cient to  place  the  alloy  in  water 
or  brine  in  a  test-tube  which  is 
immersed  in  a  beaker  of  similar 
fluid,  then,  by  raising  the  heat 
gradually  with  constant  stirring 
and  by  taking  the  mean  of  two  or 
three  determinations,  fairly  ac- 
curate results  are  obtained. 

Solders. 
Solders  are  alloys  used  in  join- 

-  Fig.  9.  —  Apparatus  for  Taking 

mg  pieces  of  metal  of  the  same  Melting-Point. 

or  of  different  kinds.     One  of  the 

constituent  metals  of  the  alloy  forming  the  solder  is  usually  the 

same  as  the  surface  upon  which  it  is  to  be  used,   hence  the 

various    metals    require    solders    of    special    composition;    for 

instance,    common    solder    is    entirely   unsuited   for    soldering 

aluminium  or  gold. 

Common  Solder  is  composed  of  tin  and  lead  in  different 
proportions.  The  larger  the  proportion  of  tin  the  finer  is  the 
solder,  and  the  following  three  grades  may  usually  be  obtained: 
"Fine"  or  "hard"  (tin  two  parts  and  lead  one),  "Common"  or 
"medium"  (tin  and  lead  equal  parts),  "  Coarse"  or  "soft"  (tin 
one  part  and  lead  two  parts). 


128  DENTAL  METALLURGY 

In  soldering  metals,  it  is  absolutely  essential  that  the  sur- 
faces be  kept  clean  and  free  from  superficial  coating  of  oxids 
which  may  form  easily  with  the  elevated  temperature  employed 
in  the  process.  Soldering  acid  and  the  various  fluxes  serve  this 
purpose.  Soldering  acid  is  an  acid  solution  of  zinc  chlorid 
usually  made  by  taking  a  few  ounces  of  strong  hydrochloric 
acid  and  adding  zinc  as  long  as  the  metal  dissolves.  Among 
the  substances  which  may  be  used  as  a  flux  to  prevent  oxi- 
dation, rosin  and  borax  are  the  most  common. 

Soft  Solders  are  those  fusing  below  a  red  heat  and  include 
the  common  solders  above  mentioned,  also  the  most  fusible 
solders  containing  bismuth.  These  last  are  more  properly 
fusible  metals  and  are  discussed  under  that  head. 

Solders  for  Aluminium.  —  Aluminium  solders  with  consider- 
able difficulty  owing  in  part  to  the  low  melting-point  of  the 
metal,  also  to  the  fact  that  aluminium  is  attacked  by  alkalis, 
including  borax,  which  makes  it  necessary  to  find  some  sub- 
stitute for  this  convenient  flux.  Essig  recommends  a  flux  con- 
sisting of  three  parts  of  copaiba  balsam,  one  part  of  Venetian 
turpentine,  and  a  few  drops  of  lemon-juice.  The  mixture  is  to 
be  used  in  the  same  manner  as  soldering  acid  with  a  solder  con- 
sisting of  zinc  from  80  to  92  parts,  aluminium  from  8  to  20 
parts.  Fused  and  finely  powdered  silver  chlorid  may  also  be 
used  as  a  flux,  the  salt  being  reduced  and  the  silver  forming  a 
superficial  alloy.  Richards  recommends  a  solder  for  aluminium 
consisting  of  tin  29  parts,  zinc  11  parts,  aluminium  i  part,  phos- 
phor-tin I  part. 

Hall  says  that  a  solder  which  he  has  found  very  satisfactory 
may  be  prepared  from  aluminium  45  parts,  tin  45,  mercury  10; 
further,  that  the  following  formulae  suggested  by  Schlosser  are 
particularly  adapted  to  soldering  dental  work  since  they  resist 
the  reaction  of  corrosive  substances. 


FUSIBLE  METALS  AND  SOLDERS  1 29 

Platinum-Aluminium  Gold-Aluminium 

Solder.  Solder. 

Gold 3     parts  Gold 5  parts 

Platinum o.i  part  Copper i  part 

Silver 2     parts  Silver i     " 

Aluminium 10       "  Aluminium 2  parts 

For  soldering  articles  of  aluminium  the  following  solder  is 
given  in  the  Pharmaceutical  Era,  January  10,  1895:  Silver  2, 
nickel  5,  aluminium  9,  tin  34,  and  zinc  50  parts,  to  be  used 
without  flux.     See  also  Dental  Cosmos  for  1906  (page  115). 

Solder  for  brass  requires  a  high  heat  for  fusion  and  on 
this  account  is- known  as  hard  solder. 

Edwinson  gives  the  following  formulas:  (i)  copper  13  parts, 
silver  11;  (2)  copper  i  part,  brass  i,  silver  19;  (3)  brass  5  parts, 
zinc  5,  silver  5.  The  flux  for  brass  soldering  is  powdered  borax, 
which  may  be  mixed  with  water  to  a  paste  and  applied  with  a 
feather  or  a  small  brush. 

Solder  for  Gold.  —  Gold  soldering  is  the  most  particular 
work  of  this  class  which  the  dentist  has  to  do.  There  are  a 
few  requirements  for  a  good  gold  solder  which  might  be  noted 
and  which  are  also  applicable  to  the  other  solders  mentioned: 
(i)  The  color  should  be  as  nearly  as  possible  that  of  the  metals 
upon  which  it  is  to  be  used.  (2)  The  solder  should  have  a 
fusing-point  but  very  sHghtly  below  that  of  the  metal  to  be 
soldered.     (3)  The  solder  should  flow  freely. 

Litch  gives  the  following  instructions  for  making  a  zinc-gold 
solder  which  will  have  the  above-mentioned  properties: 

"To  make  the  zinc-gold  solder  take  i  pennyweight  of  the 
same  gold  upon  which  it  is  to  be  used  and  add  i|  grains  of  zinc. 
If  this  is  done  in  a  crucible  in  the  furnace,  first  fuse  the  gold 
(which  should  either  be  clean  scraps  or  be  cut  from  the  plate; 
never  use  filings  for  this  purpose),  using  but  little  borax;  when 
thoroughly  fused  take  the  crucible  in  the  tongs,  drop  the  zinc 
into  it,  give  the  crucible  a  rather  vigorous  yet  skilful  shake  to 
assist  in  mixing  its  contents,  but  without  causing  any  to  be 


130  DENTAL  METALLURGY 

thrown  out,  and  immediately  pour  into  the  previously  prepared 
ingot  mold.  This  must  be  done  very  quickly  or  the  solder  will 
require  too  high  a  heat  for  the  fusion  on  account  of  a  large  pro- 
portion of  the  zinc  being  volatilized  or  oxidized  and  thus  be  lost 
as  alloys  " 

Essig  gives  the  following  f ormulge  for  alloys  of  gold  employed 
in  dentistry  as  solders: 

No.  I.     14  Carats  Fine.  No.  2.     14  Carats  Fine. 

American  gold  coin $10.00  American  gold  coin  .     16  dwts 

Pure  silver 4  dwts.  Pure  copper 3       "     18  grs. 

Pure  copper 2      "  Pure  silver 5       " 

No.  3.     14  Carats  Fine.  No.  4.     15  Carats  Fine. 

Pure  silver 2I  dwts.  Gold  coin 6  dwts. 

Pure  copper 20      grs.  Pure  silver 30  grs 

Pure  zinc 35        "  Pure  copper 20     " 

i8-carat  gold  plate  (formula  Brass 10     " 

No.  ii) 20  dwts. 

No.  5.     16  Carats  Fine.  No.  6.     16  Carats  Fine. 

Pure  gold n  dwts.  Pure  gold 11  dwts.  12  grs 

Pure  silver 3      "6  grs.  Pure  copper i  dwt.    12    " 

Pure  copper 2      "  6   "  Pure  silver 3  dwts. 

Pure  zinc 12  grs. 

No.  7.     18  Carats  Fine. 

Gold  coin 3°  parts 

Pure  silver 4 

Pure  copper i  part 

Brass i 

No.  8.     20  Carats  Fine,  tor  Crown  and  Bridge  Work. 

American  gold  coin  (21.6  carats  fine)  $10  piece 258       grs. 

Spelter  solder 20.64    " 

No.  9.     20  Carats  Fine,  Same  Use  as  No.  8. 

Pure  gold 5  dwts. 

Pure  copper 6  grs. 

Pure  silver 12 

Spelter  solder 6 


FUSIBLE  METALS   AND  SOLDERS  I3I 

No.  10.     20  Carats  Fine,  for  Crown  and  Bridge  Work. 

Zinc i|  grs. 

Pure  gold 20 

Silver  solder 3      " 

No.  II.    Dr.  C.  M.  Richmond's  Solder  for  Bridge  Work. 

Gold  coin 5  dwts. 

Fine  brass  wire i  dwt. 

No.  12.    Dr.  Low's  Formula  for  Solder  for  Crown  and  Bridge 
Work,  19  Carats  Fine. 

Coin  gold I  dwt. 

Copper 2  grs. 

Silver 4   " 

Solder  for  Platinum.  —  Platinum  utensils  may  be  soldered 
with  any  good  gold  solder,  and  a  flux  may  be  used  if  desired. 
When,  however,  the  solder  is  used  in  connection  with  porce- 
lain work,  it  must  be  pure  gold  or  a  gold  and  platinum  alloy. 
A  25%  platinum  alloy  has  been  found  to  give  excellent  results. 
The  following  in  regard  to  gold  and  platinum  alloy  is  from  the 
Dental  Review,  August,  1905: 

"The  colleges  and  text-books  tell  us  the  proper  proportions  of 
gold  and  platinum  alloys,  but  they  usually  fail  to  tell  us  how 
to  do  it.  In  most  cases  the  platinum  appears  in  white  spots  on 
the  plate  without  producing  a  proper  alloy.  Take  a  small 
piece  of  22-carat  gold  and  fuse  it  under  the  blowpipe.  Then 
work  in  all  the  platinum  you  can  in  small  pieces  until  it  has  taken 
up  all  that  is  required.  It  will  produce  a  small  button  of  a  white 
alloy  which  is  very  brittle.  Add  this  alloy  in  required  propor- 
tions to  the  gold  in  the  crucible  and  it  will  produce  a  real  platinum 
alloy.  By  this  method  you  can  make  clasp  gold  that  is  pretty 
nearly  as  stiff  as  a  steel  spring  and  yet  will  roll  and  work  with- 
out fracture.     (Mark  G.  McElhinney,  Ottawa,  Canada.) " 

Solder  for  Silver.  —  Solder  for  silver  usually  consists  of 
alloys  of  silver  and  copper  with  sometimes  zinc  and  sometimes 
tin.     Litch  recommends  a  silver  solder  made  by  alloying  pure 


132  DENTAL  METALLURGY 

silver  with  one-third  its  weight  of  brass.  ''Brannt's  Metallic 
Alloys"  give  alloys  of  silver  and  copper  simply.  Hall  recom- 
mends silver  8  parts,  copper  i,  and  zinc  2.  In  the  preparation 
of  solder  containing  copper,  zinc,  or  tin,  the  use  of  a  flux  is 
necessary  to  prevent  the  formation  of  metallic  oxid.  For  this 
purpose  borax  is  usually  employed.  The  silver,  constituting,  as 
it  does,  the  greater  proportion  of  the  alloy,  should  be  melted 
first  and  be  covered  with  considerable  borax.  When  this  has 
been  thoroughly  fused,  the  other  metals  may  be  added  and 
mixed  by  agitation  or  by  stirring  with  wood.  Finally,  the 
solder  may  be  cast  in  the  usual  ingot  mold. 


CHAPTER  XVI. 
RECOVERY   OF   RESIDUE. 

Gold.  —  The  gold  scrap  may  be  recovered  in  two  ways: 
first,  by  fusion  with  suitable  flux;  second,  by  dissolving  in  aqua 
regia  and  precipitation  of  the  metal.  In  the  first  method  it 
is  necessary  to  remove  mechanically  the  impurities  as  far  as  pos- 
sible, then  mix  the  fairly  clean  gold  waste  with  potassium  nitrate 
and  a  little  borax,  and  fuse  in  a  clay  crucible.  The  gold  will 
separate  as  a  button  at  the  bottom  of  the  thoroughly  fused  slag. 

In  the  second  method  the  scrap  gold  is  dissolved  in  aqua 
regia  and  the  resulting  solution  of  AuCls  is  precipitated  with 
ferrous  sulphate  or  oxalic  acid.  The  later  precipitant,  although 
working  more  slowly  than  the  iron,  does  not  precipitate  platinum, 
hence  in  case  platinum  is  present  it  is  the  better  reagent  to  use. 
The  precipitated  gold  is  next  filtered,  thoroughly  washed,  and 
fused  in  clay  crucible  under  borax  and  potassium  nitrate. 

Silver.  —  The  recovery  of  silver  is  best  accomplished  by 
dissolving  the  scrap  or  waste  in  nitric  acid  and  precipitating  as 
chlorid,  then  reducing  the  chlorid  to  metallic  silver  either  by 
treatment  with  pure  zinc  or  by  fusion  with  sodium  carbonate. 
If  tin  is  present  in  the  scrap,  the  nitric  acid  will  form  metastannic 
acid,  a  white  insoluble  powder  rather  difficult  to  filter.  Hence, 
it  is  better  to  wash  this  by  decantation  several  times  with  dis- 
tilled water,  which  will  remove  practically  all  the  silver.  From 
the  nitric-acid  solution  the  Ag  may  be  precipitated  by  salt  or 
hydrochloric  acid.  This  precipitate  must  be  washed  till  the 
wash-water  is  practically  free  from  chlorin,  then  dried  and  fused 
with  sodium  carbonate,  when  a  button  of  pure  silver  will  be 
obtained. 

133 


134  DENTAL  METALLURGY 

If  preferred,  the  precipitated  chlorid  of  silver  may  be  washed 
once  by  decantation,  then  agitated  with  pure  zinc,  when  the 
following  reaction  takes  place : 

2  AgCl  +  Zn  =  ZnCl2  +  2  Ag. 

The  finely  divided  Ag  (in  the  form  of  nearly  black  powder) 
must  be  washed  free  from  chlorin,  carefully  dried  and  fused 
under  carbonate  of  sodium,  or,  after  drying,  it  may  be  weighed 
and  dissolved  at  once  if  a  solution  is  desired.  If  the  silver  residue 
contains  mercury  this  may  be  driven  off  by  heat  before  solution 
is  attempted. 

Mercury.  —  Mercury  which  has  been  used  in  making  amal- 
gams is  best  purified  by  distillation.  Mercury  which  needs 
simply  to  be  freed  from  dirt,  dust,  or  slight  traces  of  other 
metals  may  be  purified  as  follows :  If  a  piece  of  filter-paper  is 
fitted  closely  in  a  glass  funnel,  a  pin-hole  made  in  the  joint  and 
the  paper  thoroughly  wetted  with  water  and  the  mercury  to  be 
purified  placed  on  the  paper,  the  heavy  metal  will  run  through 
the  pin-hole,  leaving  practically  all  the  dirt  clinging  to  the  wet 
filter-paper.  Such  mercury  may  also  be  cleansed  by  filtering 
through  chamois-skin. 

In  case  the  mercury  contains  slight  amounts  of  other  metals, 
if  it  is  digested  with  a  very  dilute  nitric  acid,  the  acid  will  gen- 
erally first  dissolve  the  impurities  and  afterwards  a  little  of  the 
mercury  itself.  Then  thorough  washing  with  water  will  remove 
all  excess  of  acid  and  all  soluble  salts  which  may  have  been 
formed.  Pure  mercury  should  have  no  coating  of  any  sort  on 
its  surface,  and  if  a  few  globules  are  allowed  to  run  down  a 
smooth  inclined  plane,  they  should  leave  no  "tail"  behind. 

Laboeatory  Exercises  XXX  to  XXXIV. 

During  the  study  of  alloys  and  volumetric  analysis  the 
student  will  be  required  to  make  quaHtative  analyses  of  several 
commercial  alloys,  dental  cements,  etc.     He  will  also  have  to 


RECOVERY  OF  RESIDUE 


135 


prepare  and  test  carefully  six  alloys,  the  formulae  for  which  will 
be  given  on  a  mimeograph  sheet  similar  to  that  represented 
below. 

The  properties  of  the  various  alloys  are  to  be  carefully  com- 
pared and  it  is  often  desirable  for  two  or  more  students  to  vary 
a  given  formula  in  some  one  particular  and  note  the  result  of 
such  a  variation  upon  the  properties  of  the  amalgam  obtained. 


ALLOYS. 


Date. 


Desk  No Name. 


No.  I. 

No.  2. 

No.  3. 

No.  4. 

No.  5- 

No.  6. 

Gold 

Silver 

18 

60 

55 

Tin 

3 

I 

65 

40 

37 

Copper 

4 

Zinc 

4 

Lead 

5 

2 

Antimony 

17 

Bismuth 

8 

4 

Cadmium 

I 

136  DENTAL  METALLURGY 

Nos.  I  and  2  contain  lead  and  must  not  tinder  any  circumstances  be  made 
in  the  graphite  crucible  which  you  intend  to  use  for  silver-tin  alloys.  These 
are  solders  or  fusible  metals.  Make  8  to  10  grams  and  determine  melting- 
point  of  each. 

No.  3  is  a  very  low  grade  dental  alloy.  Make  10  grams  and  test  for 
expansion,  discoloration,  and  crushing  strength. 

Nos.  4  and  5  are  better-grade  alloys.  Make  10  or  12  grams  of  each. 
Hand  one  in  as  sample  of  work;  test  the  other,  annealed  and  unannealed, 
as  No.  3  was  tested. 

No.  6,  your  own  formula.  Make  15  to  20  grams.  Make  complete  tests 
and  also  return  sample.  Return  all  remaining  portions  of  alloys  with  desk 
number  and  composition  of  the  alloy  plainly  written  on  envelopes  furnished, 
in  order  to  obtain  proper  credit  for  the  work. 


PART    III. 
VOLUMETRIC  ANALYSIS. 

CHAPTER  XVII. 
STANDARD    SOLUTIONS. 

Volumetric  analysis  is  the  determination  of  the  quantity 
of  a  particular  substance  contained  in  a  given  sample  by  means 
of  volumetric  or  standard  solutions.  By  means  of  standard 
solutions,  it  is  possible  to  determine  easily  and  quickly  the 
strength  of  a  peroxid  of  hydrogen  solution,  the  percentage  of 
silver  in  an  amalgam  alloy,  or  the  amount  of  gold  in  a  plate 
or  solder,  and  it  is  volumetric  analysis  thus  specialized  and 
adapted  to  dental  purposes  that  we  shall  consider. 

The  standard  solution  may  be  so  prepared  that  it  has  an 
arbitrary  or  special  value,  such,  for  instance,  as  the  silver-nitrate 
solution  usually  used  in  determining  the  amount  of  chlorin 
in  urine,  i  c.c.  of  this  solution  being  equal  to  lo  milhgrams  of 
salt  (NaCl) ;  or  its  standardization  may  be  made  with  reference 
to  the  molecular  weights  of  the  reagents  employed,  so  that  solu- 
tions of  a  similar  nature  will  be  of  equivalent  values.  That  is, 
a  solution  containing  the  hydrogen  equivalent  of  the  reagent, 
weighed  in  grams,  per  liter,  is  known  as  a  normal  solution  and 
lo  c.c.  of  any  normal  acid  will  be  of  the  same  value  in  neutralizing 
an  alkah  as  lo  c.c.  of  any  other  normal  acid.  On  the  other 
hand,  lo  c.c.  of  a  normal  acid  is  equal  to  lo  c.c.  of  any  normal 
alkali  solution  whatever  the  alkali  may  be. 

The  normal  factor  is  the  weight  of  reagent  contained  in  one 
cubic  centimeter  of  the  normal  solution. 

137 


138  VOLUMETRIC  ANALYSIS 

The  volumetric  process  and  the  use  of  the  normal  factor 
will  be  most  clearly  understood  by  the  explanation  of  a  specific 
example. 

We  will  suppose  that  we  have  prepared  a  normal  solution  of 
NaOH  and  wish  to  ascertain  the  strength  of  a  sample  of  dilute 
HCl.  The  normal  solution  will  contain  the  molecular  weight 
in  grams  of  NaOH  per  liter  or  40  grams  absolute  NaOH. 

The  molecular  weight  of  HCl  being  36.4  (36.37),  a  normal 
solution  of  HCl  will  contain  36.4  grams  absolute  HCl;  and,  if 
a  liter  of  normal  NaOH  were  added  to  a  liter  of  normal  HCl, 
exact  neutralization  would  result: 

NaOH  +  HCl  =  NaCl  +  H2O. 
40         36.4       58.4  18 

The  I  liter  of  normal  alkali  (containing  40  grams  NaOH) 
is  exactly  neutralized  by  36.4  grams  of  HCl,  or  i  c.c.  of  normal 
alkali  by  0.0364  gram  of  HCl.     0.0364  is  normal  factor  of  HCl. 

Now,  if  by  our  process  of  analysis  we  find  that  it  takes  just 
21  c.c.  of  the  NaOH  solution  to  exactly  neutralize  10  c.c.  of 
HCl  solution,  i  c.c.  of  NaOH  being  equal  to  0.0364  gram  HCl, 
21  c.c.  of  NaOH  will  be  equal  to  0.0364  X  21,  or  0.7644  gram 
HCl,  or  10  c.c.  of  the  HCl  solution  contains  0.7644  gram  of 
absolute  HCl,  equivalent,  approximately,  to  7.64%. 

It  has  become  apparent  that  in  carrying  out  this  process 
three  things  are  absolutely  necessary: 

1.  Methods  for  the  preparation  of  standard  solutions. 

2 .  Apparatus  for  accurate  measurements  of  both  the  standard 
solution  and  the  unknown. 

3.  Means  for  determining  just  when  the  point  of  exact 
neutralization  is  reached.  This  point  is  known  as  the  "end 
point"  and  is  shown  by  "indicators"  of  various  kinds. 

Preparation  of  Standard  Solutions.  —  Experience  has  shown 
that  normal  solutions  are  in  many  cases  less  convenient  to  work 
with  than  those  much  more  dilute,  both  on  account  of  the  keep- 


STANDARD  SOLUTIONS  139 

ing  qualities  of  the  standard  solution  and  the  accuracy  of  manip- 
ulation ;  and,  for  the  purposes  of  dental  chemistry,  a  decinormal  or 
one- tenth  normal  solution  represented  by  N/io  will  generally  be 
used. 

In  working  with  an  N/io  solution,  the  factor  used  in  cal- 
culations of  results  will  be  one-tenth  of  the  normal  factor  and 
is  termed  an  N/10  factor.  Other  fractional  proportions  of  the 
normal  solution  may  be  used  as  the  centinormal,  N/ioo,  or 
seminormal,  N/2.  While  the  decinormal  solution  contains 
one-tenth  of  the  hydrogen  equivalent  of  reagent  in  grams  per 
liter,  and  this  amount  is  very  easy  to  calculate,  it  is  often  very 
difficult  to  weigh  out  the  exact  amount  required.  For  instance, 
we  want  an  N/io  solution  of  HCl.  HCl  is  a  gas  soluble  in 
water  and  the  strengths  of  the  solutions  vary  greatly,  so  we  can- 
not weigh  out  3.637  grams  of  absolute  HCl  to  put  in  1000  c.c.  of 
water  though  we  know  this  is  just  the  amount  necessary  to 
produce  our  N/io  solution.  Thus,  one  of  the  first  practical 
difficulties  in  making  up  standard  solutions  is  to  find  some 
substance  which  can  be  weighed  accurately  and  the  exact  chemi- 
cal composition  of  which  may  be  relied  upon. 

Crystallized  oxalic  acid  is  such  a  compound,  although  care 
must  be  taken  that  the  crystals  are  dry  and  yet  contain  all 
their  water  of  crystallization;  in  other  words,  are  actually 
represented  by  the  formula  H2C2O4, 2  H2O.  Fused  carbonate 
of  sodium  is  another  such  compound.  If  the  purest  obtainable 
bicarbonate  of  soda  is  fused  till  no  further  change  takes  place, 
cooled,  and  powdered,  the  product  is  pure  enough  for  the  prep- 
aration of  a  standard  solution  for  ordinary  use. 

For  the  preparation  of  volumetric  solutions  it  is  necessary  to 
have  a  balance  which  will  weigh  accurately  to  at  least  two 
decimal  points.  It  will  be  much  better  to  have  a  balance  sen- 
sitive to  one  milligram.  Balances  of  this  sort  inclosed  in  a  glass 
case  can  be  obtained  at  a  very  reasonable  price.  Fig.  10  on 
page  141  represents  such  a  balance. 


T40  VOLUMETRIC  ANALYSIS 

It  is  also  essential  to  have  flasks  capable  of  holding  loo,  250, 
500,  and  1000  c.c.  carefully  graduated  on  the  neck,  represented 
in  Fig.  II,  page  141. 

Graduated  cylinders  (Fig.  12)  are  not  so  well  suited  for  the 
preparation  of  standard  solutions,  as  the  greater  breadth  of  the 
column  of  liquid  makes  accurate  reading  much  more  difi&cult. 

Small  cylinders  of  100  c.c.  or  less  are  useful  in  making  up 
odd  amounts  of  solution. 

In  the  process  of  analysis  it  will  be  necessary  to  have  pipettes 
(Fig.  13)  measuring  5  and  10  c.c,  also  a  burette  (Fig.  14),  from 
which  the  standard  solution  may  be  used.  The  burettes  may 
be  had  in  a  variety  of  styles  and  sizes,  a  very  serviceable  one 
being  of  25  c.c.  capacity  and  graduated  in  tenths  of  a  cubic  centi- 
meter. It  may  have  a  glass  stop-cock  or  it  may  be  furnished 
with  a  glass  tip  with  rubber  connector  and  pinch-cock, 

A  set  of  measuring-instruments  which  have  been  carefully 
compared  with  one  another  should  be  kept;  that  is,  the  looo-c.c. 
flask  should  be  exactly  filled  by  taking  the  loo-c.c.  flask  full  to 
the  mark  just  10  times,  thus  enabling  one  accurately  to  take 
aliquot  parts  of  any  given  solution. 

Indicators. 

The  third  requisite  for  carrying  out  a  volumetric  process 
is  a  method  for  determining  the  end  point  of  the  reaction; 
that  is,  we  must  know  when  there  has  been  a  sufficient  quantity 
of  a  standard  solution  added  to  an  unknown  solution.  Phenol- 
phthalein  gives  a  red  color  with  alkalis,  which  is  discharged 
by  the  addition  of  acid  till  the  solution  becomes  colorless  as 
it  becomes  neutral  or  acid.  Litmus  gives  a  blue  color  with 
alkalis  and  a  red  with  acids;  Methyl  orange  can  be  used  with 
carbonates  and  mineral  acids;  it  does  not  work  so  well  with 
organic  acids.  The  color  is  pink  in  acid  and  yellow  in  alka- 
line solution.  Lacmoid  is  useful  in  cases  where  the  acid  proper- 
ties of  such  salts  as  alum  or  zinc  chlorid  might  interfere  with 


STANDARD  SOLUTIONS 


141 


Fig.  10. 


Fig.  II. 


Fig.  12. 


Fig.  13. 


Fig.  14 


142  VOLUMETRIC  ANALYSIS 

the  use  of  litmus  or  phenolphthalein.  The  different  indicators 
do  not  all  change  color  at  exactly  the  same  point  in  the  process 
of  neutralization,  and  it  is  possible  for  a  solution  to  be  alka- 
line to  litmus  and  acid  to  phenolphthalein  at  the  same  time. 
Hence  uniformity  in  the  use  of  indicators  is  desirable.  In 
physiological  chemistry,  Congo  red,  tropaeolin  oo,  and  dimethyl- 
aminoazobenzol  are  also  used. 

The  end  point  may  be  indicated  by  excess  of  a  standard 
solution  if  it  happens  to  be  highly  colored,  as  potassium  per- 
manganate. Thin  starch  paste  is  used  as  an  indicator  in  oper- 
ations involving  the  use  or  liberation  of  free  iodin.  Other  indi- 
cators will  be  considered  as  we  have  occasion  to  use  them  in  the 
various  analytical  processes. 

The  process  of  volumetric  analysis  may  be  divided  into 
three  classes:  First,  acidimetry  and  alkalimetry.  Second,  oxi- 
dation and  reduction.     Third,  precipitation. 

Acidimetry  and  Alkalimetry. 

Acidimetry  and  alkalimetry  includes  all  standardized  solu- 
tions, either  acid  or  alkaline,  which  may  be  used  in  neutralizing 
solutions  of  imknown  strength  of  an  opposite  character.  For 
instance,  the  strength  of  vinegar  is  determined  by  neutralizing 
a  known  volume  with  standard  alkali. 

For  present  purposes  two  standard  acids  and  one  standard 
alkahne  solution  will  be  sufficient.  The  first  of  these  may  be 
decinormal  oxalic  solution  prepared  from  recently  recrystallized 
and  carefully  dried  acid.  The  composition  of  these  crystals 
should  be  H2C2O42  H2O,  having  molecular  weight  of  126.  This 
being  a  dibasic  acid  it  will  be  necessary  to  divide  the  molec- 
ular weight  by  2  for  a  decinormal  solution  and  then  again  by 
10  to  obtain  the  number  of  grams  which  must  be  dissolved  in 
I  liter  of  water.  For  class  use,  each  student  may  prepare  500  c.c. 
of  this  solution  by  dissolving  3.15  grams  of  pure  crystallized 
oxalic  acid  in  water  and  dilute  to  a  half-hter.     The  graduated 


STANDARD  SOLUTIONS  143 

flasks  are  usually  constructed  to  be  used  at  a  temperature  of 
60°  F.  or  15°  C.  and  for  accurate  work  solutions  must  be  brought 
to  this  temperature.  After  the  oxaHc  acid  solution  has  been 
prepared  the  decinormal  alkali  may  be  made  as  follows: 

Weigh  out  carefully  2^  grams  of  caustic  soda  or  3  grams 
of  caustic  potash  and  dissolve  in  less  than  500  c.c.  of  dis- 
tilled water.  After  the  solution  has  thoroughly  cooled,  fill  a 
burette  with  it.  Place  10  c.c.  of  standard  acid  previously 
prepared  in  a  white  porcelain  dish  of  about  250  c.c.  capacity, 
add  50  c.c.  distilled  water  and  2  or  3  drops  of  phenolphthalein 
(2%  phenolphthalein  in  alcohol  and  water,  equal  parts);  then 
carefully  run  in  from  the  burette,  with  constant  stirring,  the 
alkali  solution  until  a  permanent  pink  tint  is  produced. 

The  work  will  be  more  satisfactory  if  the  titration  is  made 
for  the  appearance  of  color  rather  than  the  disappearance  of 
color,  as  would  have  been  the  case  had  the  standard  acid  run 
into  the  measured  alkali  solution.  This  process  is  known  as 
"titration,"  and  will  hereafter  be  so  designated. 

The  Calculation. — Supposing  it  has  taken  8.2  c.c.  of  the  alkaU 
to  exactly  neutralize  the  10  c.c.  of  N/io  acid,  it  follows  that 
in  the  8.2  c.c  there  is  sufl&cient  alkali  to  equal  or  to  make  10  c.c. 
of  an  N/io  alkali  solution;  hence  we  may  add  i.S  c.c.  of  dis- 
tilled water  to  every  8.2  c.c.  of  alkaH  solution,  thereby  reducing 
it  to  decinormal  strength.  Practically  we  should  take  410  c.c. 
of  alkaU  solution  and  in  a  graduated  flask  make  it  up  to  500  c.c. 
with  distilled  water.  It  will  be  necessary  to  make  several 
titrations  and  average  the  results  before  making  the  calculation. 

From  the  standard  alkah  N/io  solutions  of  HCl  or  H2SO4 
may  be  prepared  in  a  similar  manner,  it  being  impossible  to 
accurately  weigh  either  of  these  two  acids.  In  titrating  a  car- 
bonate, if  an  indicator,  such  as  phenolphthalein,  which  is  sensi- 
tive to  carbonic  acid,  is  used,  it  is  necessary  to  keep  the  solution 
at  a  boiling  temperature  or  at  least  bring  it  to  a  boil  after  every 
addition  from  the  burette. 


144  VOLUMETRIC  ANALYSIS 

EXAMPLE   OF   ACIDIMETRY  AND   ALKALIMETRY. 

Determine  the  strength  of  a  sample  of  vinegar  as  follows: 
Measure  accurately  into  a  white  porcelain  dish  of  150-250 
c.c.  capacity  i  c.c.  of  the  sample.  This  may  be  measured  either 
with  a  carefully  graduated  i-c.c.  pipette  or  more  accurately 
by  diluting  10  c.c.  of  the  sample  to  100  c.c.  in  a  graduated  flask, 
then  using  10  c.c.  of  the  dilution  for  the  titration,  the  titration 
to  be  performed  with  N/io  NaOH,  using  phenolphthalein  as  an 
indicator. 

The  molecular  weight  of  acetic  acid  is,  in  round  numbers, 
60;  hence  the  N/io  factor  of  acetic  acid  will  be  0.006  (acetic 
acid  being  monobasic,  HC2H3O2).  To  ascertain  the  strength 
of  the  sample  of  vinegar  it  is  necessary  to  multiply  the  number 
of  cubic  centimeters  used  by  this  factor,  0.006,  which  will  give 
the  amount  of  absolute  acid  calculated  as  acetic  in  i  c.c.  (prac- 
tically I  gram)  of  the  sample.  Thus,  if  8  c.c.  of  N/io  alkali 
were  required  to  neutralize  i  c.c  of  vinegar,  multiplying  the 
factor  0.006  by  8  would  give  0.048  gram  of  absolute  acetic  acid 
in  I  c.c.  of  vinegar,  which  is  equivalent  to  4.8%. 

Carbonate  Titration. 

While  perhaps  phenolphthalein  is  the  most  serviceable  of  all 
indicators  in  common  use,  it  is  so  sensitive  to  carbon  dioxid  that 
any  titration  which  results  in  the  liberation  of  CO2  must  be 
modified  by  boiling  the  solution  thoroughly  after  each  addition 
of  acid.  This  makes  the  operation  somewhat  tedious,  but  it  is 
to  be  preferred  to  the  use  of  other  and  less  sensitive  indicators 
which  may  not  be  affected  by  the  carbon  dioxid. 

Analysis  by  Oxldation  and  Reduction. 

If  to  a  hot  solution  of  oxalic  acid  containing  sulphuric  acid, 
permanganate  of  potash  be  added,  the  following  reaction  takes 
place: 


STANDARD  SOLUTIONS  145 

2  KMn04  +  5  H2C2O4  +  3  H2SO4  =  K2SO4  +  2  MnS04 
+  10  CO2  +  8  H2O. 

This  reaction  represents  a  very  valuable  method  of  volumetric 
analysis;  but,  inasmuch  as  it  is  not  a  process  of  neutralization, 
it  cannot  properly  come  under  the  head  of  acidimetry  and  alka- 
hmetry,  but  rather  under  a  distinct  classification,  the  determina- 
tion involving  oxidation  and  reduction. 

Standard  Permanganate  Solution.  —  In  the  reaction  given 
above  we  may  consider  that,  as  the  molecule  of  K2Mn208  breaks 
up,  three  of  the  eight  atoms  of  oxygen  are  required  to  form  the 
basic  oxids  K2O  and  2  MnO  (soluble  in  the  acid  as  K2SO4  and 
2  MnS04),  while  the  remaining  five  atoms  are  liberated  and 
constitute  the  active  chemical  agent  whereby  the  oxalic  acid  is 
oxidized  to  CO2  and  H2O.  Hence,  to  reduce  this  double  molec- 
ular weight  (316)  to  the  hydrogen  equivalent  necessary  for  a 
normal  solution,  it  is  divided  by  10  (five  atoms  of  oxygen  having 
a  valence  of  10). 

The  Decinormal  Solution  may  be  made  by  dissolving  3.16 
grams  of  pure  recrystallized  and  thoroughly  dried  crystals,  if 
they  can  be  obtained,  in  distilled  water,  and  making  the  solu- 
tion up  to  1000  c.c,  or  it  may  be  standardized  by  titration  with 
the  N/io  oxalic  acid  previously  prepared;  in  this  case  one  would 
proceed  as  follows: 

Make  a  solution  slightly  stronger  than  the  standard  required, 
say  about  3.5  grams  of  the  ordinary  pure  crystals  in  a  liter  of 
water;  with  this  fill  a  burette,  place  10  c.c.  of  N/io  oxahc  acid 
measured  from  a  pipette  in  an  evaporating-dish  or  casserole, 
dilute  with  about  50  c.c.  of  water,  add  about  10  c.c.  of  dilute 
sulphuric  acid,  and  heat  the  mixture  nearly  to  the  boiling-point. 
Then  titrate  with  the  permanganate  from  the  burette.  The 
permanganate  will  at  first  be  rapidly  decolorized,  but  as  the 
operation  progresses  the  color  fades  more  slowly  till  at  last  a 
faint  permanent  pink  color  indicates  that  the  "end  point"  has 
been  reached. 


146  VOLUMETRIC  ANALYSIS 

The  temperature  must  be  kept  above  60°  C.  throughout  the 
titration  or  the  oxidation  will  take  place  too  slowly  and  an 
apparent  end  point  will  be  obtained  before  the  reaction  is  com- 
pleted. 

If  the  solution  turns  muddy  during  the  operation,  it  is  due 
to  an  insufficient  amount  of  sulphuric  acid  and  more  should 
be  added.  The  calculation  is  made  as  in  the  case  of  the  N/io 
NaOH  described  on  page  143.  The  standard  permanganate 
should  be  preserved  in  full,  well-stoppered  bottles  and  kept 
in  a  dark  place. 

It  is  better  to  have  the  KMn04  solution  made  up  a  day  or 
two  before  it  is  standardized,  thereby  oxidizing  traces  of  am- 
monia, etc.,  which  the  water  may  contain. 

DETERMINATION   OF   PEROXID    OF  HYDROGEN. 

In  determining  the  strength  of  peroxid  use  i  c.c.  of  the 
sample  measured  as  in  the  case  of  vinegar  (which  see),  dilute 
with  50  c.c.  of  distilled  water,  add  10  c.c.  of  dilute  sulphuric 
acid,  and  titrate  with  the  permanganate  in  exactly  the  same 
manner  as  detailed  in  the  preceding  paragraph,  the  reaction  in 
this  case  being  as  follows: 

2  KMn04  +  5  H2O2+3  H2S04  =  K2S04  +  2  MnS04  +  5  O2+8H2O. 

The  aqueous  solutions  of  peroxid  on  the  market  used  as 
antiseptics  contain  about  3%  absolute  H2O2  and  yield  approxi- 
mately ten  volumes  of  available  oxygen;  that  is,  10  c.c.  of  solu- 
tion will  yield  100  c.c.  of  oxygen.  The  calculation  may  be 
made  to  express  strength  of  the  peroxid  in  terms  of  percentage 
of  absolute  H2O2  by  multiplying  the  number  of  cubic  centimeters 
of  N/io  KMn04  decolorized  by  i  c.c.  of  solution  by  0.17,  or  to 
express  the  strength  in  volumes  of  available  oxygen  by  multiply- 
ing the  number  of  cubic  centimeters  of  solution  by  0.56  (more 
accurately  0.5594). 


STANDARD  SOLUTIONS  147 

DECINORMAL    lODIN. 

A  decinormal  solution  of  iodin  may  be  prepared  by  dis- 
solving 12.68  grams  of  pure  iodin  crystals  in  one  liter  of  water 
by  the  aid  of  about  18  grams  of  pure  potassium  iodid. 

Iodin  of  sufficient  purity  may  be  obtained  by  carefully  re- 
subliming  selected  and  carefully  dried  crystals  of  so-called 
"chemically-pure"  iodin. 

DECINORMAL   SODIUM   THIOSULPHATE. 

Na2S203.5  H2O  =  molecular  weight,  248.24.  This  solution 
may  be  made  by  weighing  directly  24.824  grams  of  the  pure 
crystallized  salt,  dissolving  in  water  and  diluting  to  1000  c.c,  or 
it  may  be  standardized  by  titration  with  a  decinormal  iodin 
solution,  the  reaction  being  as  follows: 

2  NaaSsOs  +  2  I  =  2  Nal  +  Na2S406. 

The  indicator  used  is  a  very  dilute  starch  paste,  which  gives 
the  characteristic  blue  color  as  soon  as  free  iodin  is  in  excess. 

By  means  of  these  two  standard  solutions  (iodin  and  sodium 
thiosulphate)  a  variety  of  determinations  may  be  made  with 
great  accuracy.  Any  substance  which  will  liberate  iodin  from 
potassium  iodid  may  be  quantitated  by  adding  an  excess  of 
the  potassium  salt  and  titrating  the  free  iodin  with  thiosulphate 
solution,  using  starch  paste  as  usual  for  an  indicator. 

Peroxid  of  hydrogen  may  be  thus  determined  as  easily  as 
by  the  permanganate  method  previously  given.  The  process, 
being  that  of  Kingzett,  is  given  as  follows  by  Sutton: 

Mix  10  c.c.  of  peroxid  solution  to  be  examined  with  about 
31  c.c.  of  dilute  sulphuric  acid  (1-2)  in  a  beaker,  adding  crystals 
of  potassium  iodid  in  sufficient  quantity,  and  after  standing 
five  minutes  titrating  the  liberated  iodin  with  N/io  thiosul- 
phate and  starch.  The  peroxid  solution  should  not  exceed  the 
strength  of  two  volumes;  if  stronger,  it  must  be  diluted  pro- 
portionately before  the  analysis. 


148  VOLUMETRIC  ANALYSIS 

In  the  case  of  a  very  weak  solution  it  will  be  advisable  to 
titrate  with  N/ioo  thiosulphate. 

I  c.c.  N/io  thiosulphate  =  0.0017  gram  H2O2  or  0.0016 
gram. 

VOLUMETRIC  DETERMINATION   OF   ARSENIC. 

Mohr's  method  of  oxidation  with  iodin  is  a  practical  one. 
The  titration  is  made  with  N/io  iodin  and  starch  as  usual, 
except  that  the  solution  should  be  at  first  neutral  and  then 
about  20  c.c.  of  saturated  solution  of  sodium  bicarbonate  should 
be  added  to  every  o.i  gram  of  AS2O3  supposed  to  be  in  the  un- 
known, thus  giving  a  certain  definite  alkalinity.  If  the  solution 
is  acid,  neutrahze  with  sodium  bicarbonate,  then  make  alkaline 
with  more  bicarbonate  as  above. 

VOLUMETRIC   DETERMINATION    OF   GOLD. 
(See  also  p.  154.) 

While  gold  is  usually  determined  quantitatively  by  assay 

in  a  dry  way  (page  157)  it  may  be  determined  very  accurately 

by  titration  with  thiosulphate  solution.     Fatka  (Chem.  Zeit.) 

recommends  the  following  process  based  upon  the  facts  that 

a  neutral  solution  of  gold  salt  with  potassium  iodid  will  give 

a  greenish  precipitate.     When   an   excess   of  potassium   iodid 

is  used  no  precipitate  is  formed,  but  a  solution  of  Auls  as  AUKI4 

results.     This  is  of  a  brown  color  and  may  be  titrated  with 

N/io  thiosulphate  solution,  when  the  following  reaction  takes 

place : 

AUKI4  +  2  NasSzOs  =  AUKI2  +  2  Nal  +  Na2S406. 

Process:  10  c.c.  of  gold  solution  containing  approximately 
2%  of  gold  is  treated  with  4  grams  of  potassium  iodid  diluted 
to  100  c.c.  with  water  and  titrated  with  N/io  Na2S203  solu- 
tion, using  starch  as  an  indicator. 

Analysis  by  Precipitation. 
Because   certain   elements   possess   a    selective   affinity   for 
Other  elements  it  is  possible  to  determine  many  substances 


STANDARD  SOLUTIONS  149 

quantitatively  by  precipitation.  That  is,  if  silver  nitrate  is 
added  to  a  mixture  of  a  soluble  chlorid  and  a  chromate,  the 
chlorin  will  combine  first  with  the  silver,  forming  AgCl,  to  the 
exclusion  of  the  chromate.  After  the  last  trace  of  chlorin  has 
been  so  combined,  then  the  silver  chromate  will  be  formed, 
which  is  a  salt  with  an  intense  red  color;  hence  it  is  possible  to 
determine  the  strength  of  solutions  of  soluble  chlorids  by  titra- 
tion with  standard  AgNOs,  using  potassium  chromate  as  an  in- 
dicator. This  process  is  used  in  analysis  of  drinking-water,  of 
saliva,  and  of  urine,  but  for  each  of  these  it  is  desirable  to  have 
solutions  of  special  strength. 

A  DECINORMAL   SILVER   SOLUTION 

may  be  made  by  dissolving  17  grams  of  pure  crystallized 
AgNOs  in  a  liter  of  distilled  water,  and  with  this  a 

DECINORMAL    SODIUM    CHLORID    SOLUTION 

may  be  prepared  as  follows : 

Weigh  out  6  grams  of  the  purest  salt  obtainable  and  dis- 
solve in  approximately  i  Hter  of  distilled  water.  With  a  pipette 
measure  10  c.c.  of  this  solution  into  a  white  porcelain  dish,  dilute 
to  about  20  c.c.  with  H2O,  add  two  to  five  drops  of  neutral 
potassium  chromate  (K2Cr04)  and  add  AgNOs  from  a  burette 
till  a  faint  pink  color  persists. 

The  calculation  and  dilution  is  made  exactly  as  described 
on  page  143  in  the  preparation  of  a  standard  NaOH  solution. 
The  silver  nitrate  solution  used  to  determine  chlorin  in  urine 
is  usually  prepared  of  such  a  strength  that  i  c.c.  precipitates 
just  10  milligrams  of  sodium  chlorid.  This  is  equivalent  to 
0.006065  gram  of  chlorin.  A  solution  of  this  strength  is  pro- 
duced when  29.075  grams  of  pure,  fused  silver  nitrate  are 
dissolved  in  sufficient  distilled  water  to  measure  i  liter  of  solu- 
tion. If  chlorin  is  to  be  determined  in  drinking-water,  it  is 
usually  necessary  to  concentrate  the  water  at  least  1/5  its  bulk 


150  VOLUMETRIC  ANALYSIS 

and  then  use  not  more  than  one  or  two  drops  of  neutral  chro- 
mate  as  indicator.  The  standard  silver  nitrate  for  this  titra- 
tion should  be  very  dilute.  A  convenient  solution  may  be 
prepared  by  diluting  the  standard  AgNOa  for  urine  i  to  10. 
In  saliva  the  sample  may  be  diluted  with  an  equal  volume  of 
water  and  titrated  the  same  as  in  the  case  of  drinking-water. 
In  all  quantitative  processes  where  silver  chromate  is  used  to 
determine  the  end  point  the  solution  must  be  practically  neutral, 
as  the  formation  of  this  salt  is  prevented  by  either  acids  or  alkalis. 

Volumetric  Determination  of  Silver  by  Standard 
Potassium  Sulphocyanate  Solution. 

Silver  may  be  determined  volumetrically  in  nitric  acid 
solution  by  titration  with  standard  KCyS  solution,  using  ferric 
alum  as  an  indicator.  The  sulphocyanate  solution  must  be 
standardized  against  decinormal  AgNOs  as  follows:  Prepare  a 
solution  containing  not  less  than  10  grams  of  chemically  pure 
KCyS  per  liter.  Place  this  solution  in  the  burette  and  put  in 
the  porcelain  dish  10  c.c.  of  decinormal  AgNOs  which  has  been 
strongly  acidified  with  nitric  acid  and  15  or  20  drops  of  a  solu- 
tion of  ferric  alum,  added  as  an  indicator.  The  end  point  is 
indicated  by  the  faint  red  color  of  ferric  sulphocyanate,  pro- 
duced by  the  first  excess  of  KCyS.  The  calculation  will  be  the 
same  as  previously  described  in  the  preparation  of  N/io  NaOH 
(page  143). 

Now,  to  determine  the  silver  in  solution  of  an  alloy,  take  a 
measured  volume  of  the  filtrate,  about  30  c.c,  and  put  in  a 
porcelain  dish  and  add  the  indicator  as  above. 

Then  place  the  standard  KCyS  in  the  burette  and  titrate 
till  the  faint  red  color  is  produced. 

Suppose  8  c.c  of  KCyS  is  used.  The  weight  of  silver  in  i  c.c. 
of  a  decinormal  solution  is  0.0108  gram.  Multiplying  8  by 
0.0108  =  0.0864.  Divide  by  number  of  c.c.  of  solution  taken, 
0.0864  ^  30  =  0.00288  gram  Ag  in  i  c.c.  of  solution. 


STANDARD  SOLUTIONS  151 

Multiply  by  whole  number  of  cubic  centimeters  and  divide 
by  weight  of  alloy  taken  and  result  will  be  percentage  of  silver. 

VOLUMETRIC   DETERMINATION   OF   COPPER. 

Into  a  solution  of  copper,  free  from  other  metals  of  Group  I 
or  II,  pass  H2S  gas.  Wash  the  resulting  copper  sulphid  thor- 
oughly with  II2S  water,  and  dissolve  in  dilute  nitric  acid;  then 
wash  the  paper  in  warm  water,  add  to  the  filtrate  (wash  water) 
sodium  carbonate  until  precipitate  formed  is  nearly  dissolved; 
then  add  i  c.c.  of  dilute  NII4OH.  Titrate,  to  complete  dis- 
appearance of  blue  color,  with  KCN  solution  previously  stand- 
ardized after  this  same  method  against  pure  copper  wire.  A 
little  practice  is  required  in  determining  the  end  point  to  give 
the  process  any  degree  of  accuracy.  An  excess  of  ammonia  should 
be  avoided,  as  it  interferes  with  the  accuracy  of  the  end  point. 

VOLUMETRIC   DETERMINATION    OF    ZINC. 

The  solution  from  which  silver  and  copper  have  been  re- 
moved, together  with  all  wash- water,  may  be  concentrated; 
if  acid  in  reaction  it  should  be  evaporated  to  dryness,  and  the 
residue  dissolved  in  water;  then  add  a  fairly  strong  solution 
of  oxalic  acid  and  an  equal  volume  of  strong  alcohol.  Allow 
to  stand  15  to  30  minutes,  filter,  and  wash  with  70%  alcohol  till 
oxalic  acid  is  removed,  dry  until  the  alcohol  has  disappeared, 
dissolve  in  dilute  sulphuric  acid,  and  titrate  the  solution  with 
N/io  permanganate  and  calculate  the  zinc  from  the  amount 
of  oxalic  acid  found. 

This  method  is  usually  fully  as  satisfactory  as  the  gravi- 
metric determination  given  on  page  156. 

Volumetric  Methods  Applicable  to  Analyses  of  Saliva  or 

Urine. 
determination  of  chlorin. 
Chlorids  may  be  determined,  without  separating  other  con- 
stituents, by  titration  with  silver  nitrate,  using  neutral  potassium 


152  VOLUMETRIC  ANALYSIS 

chromate  as  an  indicator,  according  to  the  method  indicated 
on  page  149,  or  a  more  accurate  determination  may  be  made 
by  a  double  titration  as  follows:  To  5  or  10  c.c.  of  solution 
add  an  excess  (10  or  15  c.c.)  of  standardized  silver  nitrate; 
then  adding  a  httle  nitric  acid  to  prevent  precipitation  of  the 
phosphates,  etc.,  and  a  solution  of  ferric  alum  as  an  indicator, 
titrate  the  mixture  with  a  solution  of  potassium  sulphocyanate 
KCyS. 

If  the  sulphocyanate  solution  has  been  standardized,  so 
that  it  is  the  same  relative  strength  as  the  silver  nitrate  used, 
the  number  of  cubic  centimeters  of  the  KCyS  required  may  be 
subtracted  directly  from  the  number  of  cubic  centimeters  of 
AgNOs  added,  and  the  difference  will  represent  the  amount 
of  silver  nitrate  required  to  precipitate  chlorin  in  the  quantity  of 
fluid  taken. 

VOLUMETRIC   DETERMINATION   OF   CALCIUM. 

This  method  is  based  upon  that  recommended  by  Dr.  Percy 
R.  Howe,  Dental  Cosmos,  April,  191 2.  To  5  c.c.  of  saliva,  add  as 
much  more  distilled  water  and  a  slight  excess  of  oxalic  acid 
or  ammonium  oxalate  (5  c.c.  of  normal  solution  will  be  sufficient). 
Add  ammonium  water  to  alkaline  reaction,  heat  nearly  to  the 
boihng  point,  and  allow  to  stand  for  20  to  30  minutes.  Filter 
through  a  hardened  filter  pap>er  into  a  small  beaker  which  is 
allowed  to  stand  on  a  piece  of  black  glazed  paper.  Under  these 
circumstances,  a  slight  rotary  motion  of  the  beaker  will  show 
if  any  of  the  white  precipitate  of  calcium  oxalate  is  passing 
through  the  paper. 

After  filtration  is  complete,  wash  five  times  in  hot  distilled 
water;  then  place  the  precipitate,  together  with  the  paper,  into 
a  small  beaker,  add  about  30  c.c.  of  dilute  sulphuric  acid,  and 
heat  nearly  to  the  boihng  point;  then  titrate  with  N/20  perman- 
ganate solution. 


STANDARD  SOLUTIONS  153 

VOLUMETRIC  DETERMINATION   OF   PHOSPHORIC  ACID. 

The  determination  of  total  phosphoric  acid,  calculated  as 
P2O5,  requires  the  following  solutions: 

A  standard  uranium  solution,  containing  35.5  grams  of  pure 
uranium  nitrate  or  acetate  in  distilled  water  sufficient  to  make 
1000  c.c;  next  an  acid  solution  of  sodium' acetate,  containing 
10%  of  sodium  acetate  and  3%  of  acetic  acid,  and  lastly  a 
saturated  solution  of  potassium  ferrocyanide,  to  be  used  as  an 
indicator. 

Process  (as  given  by  Ogden's  Clinical  Examination  of 
Urine) :  Take  30  c.c.  of  the  urine  in  a  porcelain  evaporator, 
add  5  c.c.  of  the  sodium  acetate  solution,  and  heat  the  mixture 
to  80°  C.  over  a  water-bath.  Titrate  the  hot  mixture  slowly 
with  standard  uranium  solution  until  a  drop  from  the  evapora- 
ting dish  placed  on  a  porcelain  tile  with  a  drop  of  the  potassium 
ferrocyanide  gives  a  distinct  brown  color.  When  this  point  is 
reached  the  number  of  cubic  centimeters  of  uranium  solution 
used  is  noted  and  multiplied  by  0.005  which  will  give  the  quan- 
tity of  phosphoric  acid  in  30  c.c.  of  urine,  and  from  this  one  can 
calculate  the  percentage  of  total  phosphoric  acid. 

This  same  process  may  be  used  for  saliva  by  diluting  the 
reagent  i  part  to  5,  and  preparing  the  sample  for  titration  as 
follows:  Take  from  2  to  5  c.c.  saliva,  add  sufficient  alcohol  to 
make  10  c.c  of  mixture,  warm  and  filter.  This  serves  to  separate 
the  protein  substance.  Take  5  c.c.  of  the  filtered  solution  and 
titrate  with  the  diluted  uranium  solution  as  by  the  process  given 
above  for  urine.  In  this  case,  of  course,  i  c.c.  of  the  standard 
uranium  will  represent  i  milligram  of  P2O5  rather  than  5. 

GRAVIMETRIC  DETERMINATIONS. 

Gravimetric  determinations  are,  as  a  rule,  more  accurate 
than  volumetric;  but  they  require  greater  care  and  attention 
to  details,  making  them  less  satisfactory  in  the  hands  of  the 


154  VOLUMETRIC  ANALYSIS 

beginner.  Some  determinations,  however,  on  account  of  diffi- 
culties in  obtaining  accurate  end  points  and  absolute  separations, 
are  really  easier  when  made  by  gravimetric  processes.  A  few 
of  these  will  be  given. 

GRAVIMETRIC   DETERMINATION   OF   TIN  AS  Sn02. 

Tin  may  be  separated  from  dental  alloys  in  the  absence  of 
gold  or  platinum  by  simply  dissolving  the  alloy  in  nitric  acid. 
Tin  will  remain  as  a  white  insoluble  metastannic  acid.  As  stated 
on  page  33  metastannit  acid,  upon  long  standing,  will  change  to 
somewhat  soluble  compounds,  hence  this  operation  should  be 
completed  with  reasonable  rapidity.  After  complete  disintegra- 
tion of  the  alloy,  the  insoluble  tin  compound  may  be  separated 
by  filtration  through  asbestos  fiber,  contained  in  a  Gooch  cruci- 
ble.    The  method  of  procedure  is  as  follows: 

A  little  fine  asbestos  fiber,  washed  in  acid  and  held  in  sus- 
pension in  water,  is  placed  on  the  bottom  of  the  crucible.  The 
crucible  is  then  placed  in  the  top  of  a  filtering  flask  from  which 
the  air  is  exhausted  by  the  suction  pump.  This  packs  the 
asbestos  down  firmly  on  the  bottom  of  the  crucible  in  a  thin 
layer,  and  care  should  be  taken  that  the  quantity  of  asbestos 
used  is  such  that  water  will  pass  through  it  easily.  The  cruci- 
ble with  asbestos  is  next  dried,  ignited,  and  weighed.  Now 
transfer  the  precipitate  of  tin  oxid  (metastannic  acid)  to  the 
crucible,  taking  care  that  none  is  lost,  and  wash  thoroughly  six 
or  eight  times,  then  dry,  ignite  strongly,  and  weigh  again. 

If  the  ignited  residue,  weighed  as  tin  oxid,  does  not  contain 
gold  or  platinum,  the  weight  of  tin  may  be  obtained  by  multi- 
plying the  weight  of  the  ash  by  0.788. 

VOLUMETRIC   DETERMINATION   OF   GOLD. 

If  the  residue  of  tin  oxid  does  contain  gold,  it  should  be 
separated  and  its  weight  deducted  before  the  calculation  for 
Sn  is  made  as  above.     This  separation  may  be  made  by  the 


STANDARD  SOLUTIONS  I55 

fire  assay  as  given  on  page  157,  or  by  solution  in  aqua  regia 
and  subsequent  precipitation  with  oxalic  acid,  according  to  the 
following  method  as  given  by  Schimpf  in  his  Manual  of  Volu- 
metric Analysis. 

The  gold  must  be  in  the  form  of  chlorid  (AuCls). 

To  the  solution  of  gold  chlorid  a  measured  excess  of  N/i  oxalic 
acid  solution  is  added  and  the  mixture  set  aside  for  twenty-four 
hours. 

The  solution  is  then  made  up  to  a  definite  volume  (say  300 
c.c).  Then,  by  means  of  a  pipette,  100  c.c.  are  removed,  and 
the  excess  of  oxalic  found  by  titrating  with  N/io  permanganate 
in  the  presence  of  sulphuric  acid.     The  reaction  is 

2  AuCls  +  3  H2C2O4  =  2  Au  -1-  6  HCl-f  6  CO2. 

Each  cubic  centimeter  of  N/i  oxahc  acid  solution  =  0.06523 
gram  of  Au,  or  0.1004  gram  of  AuCls- 

GEAVIMETRIC  DETERMINATION   OF   SILVER. 

The  gravimetric  determination  of  silver  is  not  difficult,  and 
is  rather  more  accurate  than  the  volumetric  method.  The  silver 
is  obtained  in  the  form  of  AgCl.  This  is  separated  by  filtration 
through  an  ashless  paper,  and  dried.  Then  the  dried  precipitate 
is  removed  as  completely  as  possible  onto  a  square  of  black 
glazed  paper  and  preserved  under  a  funnel  or  bell  glass.  The 
filter  paper,  containing  traces  of  AgCl  which  could  not  be  re- 
moved, is  next  incinerated  in  a  previously  weighed  porcelain 
crucible. 

As  slight  reduction  of  AgCl  to  Ag  may  take  place  during 
the  ignition  of  the  paper,  it  is  necessary  to  add,  after  the  paper 
is  completely  burned,  a  drop  or  two  of  nitric  acid,  and  after  the 
excess  has  been  driven  off  by  gentle  heat,  a  drop  or  two  of  HCl. 
This  treatment  dissolves  any  reduced  silver  and  reprecipitates 
AgCl.  After  carefully  heating  to  dry  the  precipitate  in  the 
crucible,  the  reserved  portion  of  silver  chlorid  is  carefully  brushed 


156  VOLUMETRIC  ANALYSIS 

into  the  crucible  and  the  whole  ignited  until  the  silver  chlorid 
begins  to  fuse.     It  is  then  cooled  and  weighed  as  AgCl. 

GRAVIMETRIC  DETERMINATION  OF  COPPER. 

Copper  may  be  determined  quite  easily  by  electrolysis  of 
the  faintly  acid  (H2SO4)  solution.  The  copper  solution  must  be 
freed  from  other  metals  and  preferably  be  obtained  as  a  solu- 
tion of  copper  sulphate  of  approximately  o.i  of  1%  of  copper. 
50  c.c.  of  such  a  solution  are  put  into  a  platinum  dish  which 
is  placed  upon  a  copper  plate  connected  with  the  negative  pole 
of  a  battery.  A  strip  of  platinum  suspended  from  the  positive 
pole  is  immersed  in  the  solution  and  the  current  allowed  to  pass 
for  from  three  to  twelve  hours,  according  to  the  strength  of  the 
copper  solution.  The  ordinary  no- volt  (direct)  current  em- 
ployed for  electric  lighting  may  be  used  by  introducing  a  re- 
sistance of  from  three  to  six  i6-c.p.  lamps.  After  the  copper  has 
been  entirely  deposited  the  residual  solution  is  drained  out  of  the 
platinum  dish,  a  little  alcohol  added,  which  is  also  drained  out, 
and  by  setting  fire  to  the  last  traces  of  alcohol  the  precipitated 
copper  is  dried  and  in  condition  to  weigh.  Care  must  be  taken 
to  avoid  oxidation  of  the  finely  divided  Cu ;  if  it  turns  black  too 
much  heat  has  been  used  and  partial  oxidation  has  taken  place, 
which  has  of  course  resulted  in  an  increase  of  weight. 

GRAVIMETRIC   DETERMINATION   OF   ZINC. 

Zinc  may  be  determined  gravimetrically  by  precipitation  as 
zinc  sulphide  as  follows :  To  a  measured  portion  of  the  solution, 
free  from  all  metals  (except  zinc)  of  Groups  I,  II,  III,  and  IV, 
add  ammonium  chlorid,  ammonium  hydroxid,  and  ammonium 
sulphid,  as  in  qualitative  analysis.  Filter  the  precipitated  ZnS 
on  to  counterpoised  filters,  wash  thoroughly  with  water  con- 
taining a  Httle  ammonium  sulphid,  dry  in  an  atmosphere  free 
from  oxygen,  (hydrogen  or  hydrogen  sulphid),  and  weigh  as 
ZnS. 


analysis  of  alloys  1 57 

Gravimetric  Assay  of  Gold  and  Silver  in  the  Dry  Way. 

It  is  often  more  convenient  to  determine  gold  and  silver  by 
the  fire  assay  than  by  the  volumetric  methods  previously  given. 
This  is  accomplished  usually  by  fusion  with  an  excess  of  lead 
and  a  borax  flux.  The  mixture  is  kept  at  a  high  heat  for  up- 
wards of  thirty  minutes,  with  a  current  of  air  passing  over  the 
surface  of  the  molten  metals.  This  serves  to  oxidize  and  carry 
away  the  baser  metals,  leaving  the  gold  and  silver  with  but  a 
slight  amount  of  lead,  possibly  a  trace  of  copper  and  tin.  The 
purification  is  completed  by  cupellation.  When  the  traces  of 
lead  and  other  metals  are  absorbed  by  the  cupel  or  are  driven 
off  as  volatile  oxids,  the  button  of  gold  and  silver  is  next  cooled 
very  slowly  and  carefully  weighed.  From  this  the  silver  may  be 
dissolved  by  nitric  acid  unless  the  gold  is  in  considerable  excess, 
which  would  rarely  be  the  case.  If  it  happens  that  the  gold 
is  present  in  sufiicient  quantity  to  prevent  the  solution  of  the 
silver  in  nitric  acid  a  known  weight  of  pure  silver  may  be  added 
in  amount  sufficient  to, increase  the  percentage  of  silver  to  75 
or  over,  fused,  and  then  all  the  silver  dissolved  out  with  HNO3, 
leaving  the  gold. 

The  gold  which  has  resisted  solution  may  be  found  as  small 
black  particles  or  grains  in  the  bottom  of  the  crucible.  This 
should  be  carefully  washed  with  distilled  water  by  decantation, 
very  carefully  dried  and  brought  to  a  red  heat,  which  will  give 
a  button  of  pure  gold.  This  may  be  weighed  and  the  weight 
subtracted  from  the  weight  of  gold  and  silver  button  previously 
obtained. 

QUANTITATIVE  ANALYSIS  OF  DENTAL  ALLOYS  CON- 
TAINING Au,  Sn,  Ag,  Cu,  Zn. 

Weigh  accurately  0.5  of  a  gram  of  alloy  which  has  been  re- 
duced to  fine  filings  and  from  which  all  particles  of  iron  have 
been  carefully  removed  by  a  magnet,  transfer  to  a  beaker  and 


158  VOLUMETRIC  ANALYSIS 

dissolve  in  15  c.c.  of  strong  HNO3  and  10  c.c.  of  H2O  by  aid  of 
gentle  heat.  If  the  sample  contains  tin  or  gold,  complete  solu- 
tion will  not  be  effected,  but,  by  watching  the  character  of  the 
sediment  through  the  bottom  of  the  beaker,  it  is  possible  easily 
to  determine  when  the  alloy  has  been  completely  disintegrated. 

If  silver  is  to  be  determined  by  titration  with  NaCl  and 
K2Cr04,  evaporate  on  a  water-bath  till  all  nitric  acid  has  been 
expelled. 

If  silver  is  to  be  determined  by  the  sulphocyanid  solution, 
evaporation  at  this  point  is  not  necessary.  In  either  case,  make 
the  whole  solution  up  to  250  c.c.  with  distilled  water;  then  filter 
out  tin  and  gold,  following  the  method  given  under  gravimetric 
determination  of  tin  (page  154),  reserving  the  filtrate  before  any 
wash-water  has  been  added.  For  convenience  this  filtrate  may 
be  marked  "A".  Titrate  25  or  50  c.c.  of  this  filtrate  ("A") 
for  silver  (page  150.) 

Take  100  c.c.  of  filtrate  "A"  and  precipitate  silver  by  slight 
excess  of  HCl.  Filter  and  wash  precipitate  thoroughly  with 
warm  water.  Concentrate  filtrate  and  wash-water,  which  may 
be  designated  as  filtrate  "B."  Pass  H2S  gas  into  "B"  till 
copper  is  entirely  separated  as  CuS.  Filter  and  wash  CuS 
seven  or  eight  times  with  dilute  H2S  water.  Reserve  filtrate 
and  wash- water  as  filtrate  "  C".  Dissolve  CuS  in  dilute  HNO3, 
wash  paper  carefully,  concentrate  and  determine  amount  of 
copper  by  deposition  upon  platinum  (page  156).  Concentrate 
filtrate  "  C"  and  determine  Zn  by  volumetric  method  given  on 
page  151. 

During  the  study  of  volumetric  analysis,  taking  probably 
about  two  weeks'  time,  consequently  covering  twelve  Labora- 
atory  exercises  (Nos.  35  to  46  inclusive),  the  student  will  be  re- 
quired to  make  the  various  standard  solutions,  to  use  them  more 
or  less  on  solutions  of  unknown  strength,  and  to  make  a  complete 
quantitative  analysis  of  at  least  one  dental  alloy. 


PART    IV. 

MICROCHEMICAL  ANALYSIS. 

CHAPTER  XVIII. 
METHODS. 

The  advantages  of  microchemistry  are  many,  as  claimed  by 
its  enthusiastic  advocates,  and  there  are  two  particulars  in  which 
these  methods  strongly  recommend  themselves  to  the  dental 
practitioner:  (i)  Microchemical  analysis  deals  with  exceedingly 
minute  portions  of  matter,  making  the  examination  of  very 
small  particles  of  substance  easily  possible.  (2)  Three  or  four 
one-ounce  "drop-bottles"  and  a  few  two-drachm  vials  will 
contain  all  necessary  reagents,  and  in  consequence  three  feet 
of  bench-room  will  furnish  ample  laboratory  space. 

The  principles  of  microchemical  analysis  are,  of  course,  the 
same  as  for  any  analysis,  but  the  processes  employed  are  quite 
different  and  need  some  explanation.  In  microchemical  analysis 
the  production  of  crystals  of  characteristic  form  furnishes  per- 
haps the  most  rapid  method  of  detection  of  an  unknown  sub- 
stance, and  in  this  we  are  greatly  aided  by  the  use  of  polarized 
light,  which  not  only  helps  in  the  differentiation  of  crystals  but 
often  makes  it  possible  to  see  and  distinguish  small  or  trans- 
parent crystals  which  might  otherwise  escape  notice  altogether. 

Use  of  Microscope.  —  For  the  examination  of  the  crystals 
mentioned  in  this  chapter,  also  for  the  work  required  on  saliva 
or  urine,  lenses  of  comparatively  low  power  are  sufficient.  For 
most  of  the  microchemical  tests,  a  No.  3  Leitz  or  a  16  mm.  Bausch 
&  Lomb  objective  will  be  found  satisfactory.     For  a  few  micro- 

159 


l6o  MICROCHEMICAL  ANALYSIS 

chemical  tests  and  for  urine,  a  34-inch  Bausch  &  Lomb  or  a 
No.  5  Leitz  objective  will  give  better  results  in  the  hands  of  a 
beginner  than  one  of  higher  power. 

In  using  the  microscope  for  microchemistry,  the  preparation 
should  always  be  covered  with  a  cover  glass  and  the  examination 
be  made  with  the  low-power  lens  if  possible.  The  object  in 
covering  is  to  prevent  any  action  by  reagent  upon  the  objective. 
As  a  further  precaution,  it  is  well  to  form  the  habit  of  first 
lowering  the  objective  and  then  focusing  by  upward  movement 
of  the  draw-tube. 

Formation  of  crystals  may  be  brought  about  in  two  ways: 
firsts  by  precipitating  insoluble  crystalline  salts  by  use  of  re- 
agents, as  in  ordinary  qualitative  analysis;  second,  by  allowing 
salts  to  crystalHze  by  spontaneous  evaporation  of  the  solvent. 

If  the  first  method  is  to  be  employed  it  is  essential  to  have 
the  dilution  fairly  constant  in  order  to  obtain  crystals  which  shall 
be  comparable  with  those  obtained  at  other  times  or  by  other 
individuals.  The  tendency  of  strong  solution  is  to  give  amor- 
phous precipitates.  Sometimes  the  precipitate  will  be  amor- 
phous when  first  thrown  down,  but  upon  standing  will  assume 
crystalline  form.  To  secure  the  uniformity  of  results  necessary 
to  correct  deductions,  the  following  method  of  procedure  should 
be  exactly  followed  every  time. 

The  reagent  should  be  of  uniform  strength,  usually  i  or  2  per 
cent.  Place  on  a  clean  microscope-slide  a  small  drop  of  the  solu- 
tion to  be  tested,  and  as  close  as  possible  without  touching  it,  one 
of  about  equal  size  of  the  reagent  to  be  used.  Now  bring  the 
drops  together  by  tapping  the  sHde  or  with  a  small  glass  rod.  If 
a  precipitate  forms  immediately,  cover  with  a  cover-glass  (this 
must  always  be  done)  and  examine  with  the  microscope.  If  the 
precipitate  is  crystalline,  note  the  form,  and  in  any  case,  whether 
crystalline  or  not,  repeat  the  test  after  diluting  the  unknown 
solution  one-half.  If  the  second  test  gives  an  amorphous  pre- 
cipitate, or  crystals  of  different  shape  from  the  first,  continue 


METHODS  l6l 

the  dilution  of  the  unknown  till  a  point  is  reached  when  admixture 
with  the  drop  of  reagent  gives  no  immediate  precipitate,  but  one 
appearing  in  a  few  seconds'  time  (five  to  thirty).  In  this  way 
we  have  produced  the  precipitate  under  standard  conditions  or 
as  nearly  such  as  is  possible  with  unknown  solutions. 

Until  thoroughly  familiar  with  the  forms  obtained  by  drying 
the  various  reagents,  it  is  well  to  evaporate  a  small  drop  of  the 
reagent  alone,  on  the  same  slide  on  which  a  test  is  made,  for  the 
sake  of  subsequent  comparisons. 

Filtration  in  microchemical  examinations,  when  perhaps  only 
a  few  drops  of  solution  are  to  be  had,  may  be  effected  in  a  very 
satisfactory  manner  and  without  appreciable  loss  by  absorption 
as  follows: 

Cut  a  filter-paper  about  i  cm.  wide  and  6  cm.  long,  double 
it  and  crease  the  middle  so  that  it  assumes  the  shape  of  an  in- 
verted V.  Put  the  solution  to  be  filtered  in  a  small  watch- 
glass  placed  at  a  sHght  elevation  above  a  microscope  slide; 
now  place  one  "leg"  of  the  strip  of  filter-paper  in  the  watch- 
glass,  allowing  the  end  of  the  other  to  touch  the  sHde.  By 
capillary  attraction  the  clear  solution  will  follow  over  the  bend 
in  the  strip  of  paper  and  a  drop  or  two  of  perfectly  clear  filtrate 
suitable  for  the  test  will  be  found  upon  the  slide. 

Evaporation  of  a  solution  is  best  effected  on  a  small  watch- 
glass  held  in  the  fingers  and  moved  back  and  forth  over  a  low 
Bunsen  flame,  or  else  placed  over  a  water-bath. 

The  purpose  of  the  microchemical  tests  here  outHned  is  not 
so  much  a  method  of  general  qualitative  analysis,  to  which  they 
are  not  suited,  as  it  is  a  specific  application  of  well-known  reac- 
tions to  concrete  examination  of  substances,  the  uses  and  prob- 
able composition  of  which  are  known.  The  details  of  the  various 
tests  will  be  given  under  classification  furnished  by  the  sub- 
stances investigated. 

Our  study  may  include  alloys  and  amalgams,  teeth,  tartar, 
dental  anaesthetics,   cement,  mouth-washes,   antiseptics,   disin- 


l62  MICROCHEMICAL  ANALYSIS 

fectants,  and  sediments  obtained  from  the  saliva  and  from  the 
urine. 

The  following  crystals  are  selected  as  among  those  most 
frequently  met  with  in  the  analysis  of  the  above  substances  or 
best  suited  for  the  study  of  microchemical  processes,  and  the 
student  should  make  each  test  here  indicated  and  carefully 
draw  the  crystals  produced: 

1.  Calcium  oxalate  from  2%  H2C2O4  and  CaCl2  solutions 
(Plate  II,  Fig.  i). 

2.  Cadmium  oxalate  from  2%  H2C2O4  and  CdS04  solutions 
(Plate  II,  Fig.  2). 

3.  Strontium  oxalate  from  2%  H2C2O4  and  Sr(N03)2  solu- 
tions (Plate  II,  Fig.  3). 

4.  Sodium  oxalate  by  evaporation  of  aqueous  solution,  also 
by  evaporation  of  urine  containing  Na2C204  (polarized  light) 
(Plate  II,  Fig.  4). 

5.  Urea  oxalate  from  2%  H2C2O4  and  urea  solution  (Plate 

n,  Fig.  5). 

6.  Ammonium-magnesium-phosphate  from  magnesium  mix- 
ture *  and  sodium  phosphate  (Plate  IV,  Fig.  2). 

7.  Ammonium  platinic  chlorid  (Plate  III,  Fig.  i). 

8.  Ammonium  phosphomolybdate  from  ammonium  molyb- 
date  and  phosphate  of  sodium  (Plate  III,  Fig.  2). 

9.  Sodium  urate  by  evaporation  (polarized  light)  (Plate  X, 

Fig.  3.  OPP-  page  368.) 

10.  Crystals  formed  from  cocain  and  potassium  perman- 
ganate (Plate  III,  Fig.  4). 

11.  Crystals  formed  from  carbolic  acid  and  dilute  bromin 
water  (tribromphenol)  (Plate  III,  Fig.  5). 

12.  Crystals  formed  from  morphin  solutions  and  ammo- 
nia (morphia)  (Plate  III,  Fig.  6). 

*  Magnesium  mixture  as  used  in  urine  analysis  to  precipitate  phosphates 
contains  MgCla  (or  MgSOO,  NH4CI  and  NH4OH. 


PLATE  II.  — MICROCHEMICAL   ANALYSIS. 


Fig.  I. 
Calcium  Oxalate. 


Fig.  3. 
Strontium  Oxalate. 


Fig.  2. 
Cadmium  Oxalate. 


Fig.  4- 
Sodium  Oxalate  (P.L.). 


Fig.  5- 
Oxalate  of  Urea. 


Fig.  6. 
Zinc  Oxalate. 


PLATE  III.  — MICROCHEMICAL   ANALYSIS. 


Fig.  I. 
Ammonium  Platinic  Chlorid. 


Fi6.  3. 
Potassium  Platinic  Chlorid. 


Fig.  2. 
Ammonium  Phosphomolybdate. 
No.  3  and  No.  7  Leitz  Objective. 


Fig.  4. 
Cocain  and  Potassium  Permanganate. 


Fig.  5. 
Tri-brom-phenol. 


Fig.  6. 
Morphin. 


PLATE  IV— MICROCHEMICAL  ANALYSIS. 


'Fig.   I. 
Morphin  and  Marme's  Reagent. 


Fig.  2. 
Magnesium  Ammonium  Phosphate. 


Fig.  3. 
Cocain  with  Tin  Chlorid. 


Fig.  4- 
Chloretone  and  Sodium  Hypochlorite. 


Fig.  S- 
Palmitic  Acid. 


Fig.  6. 
Uranyl  Sodium  Acetate^ 


METHODS  163 

13.  Crystals  formed  from  morphin  and  Marme's  reagent 
(Plate  IV,  Fig.  i). 

14.  Crystals  formed  from  chloretone  and  sodium  hypo- 
chlorite (Plate  IV,  Fig.  4.) 

The  list  may  be  extended  to  include  the  crystals  produced 
by  various  alkaloidal  salts  with  the  common  reagents,  also  sub- 
stances usually  employed  in  the  manufacture  of  the  various 
dental  preparations. 


CHAPTER  XIX. 
LOCAL  ANESTHETICS. 

In  considering  the  chemistry  of  local  anaesthetics  we  may 
divide  them  into  two  classes  as  follows : 

First.   Those  of  definite  or  well-known  composition,  and 

Second.  Preparations  of  a  proprietary  nature,  the  compo- 
sition of  which  is  always  problematical. 

In  the  first  class  will  be  found  cocain,  eucain,  tropacocain, 
acoin,  ethyl  chlorid,  etc.,  which  will  be  later  alphabetically 
considered.  The  second  class  contains  a  large  number  of  prep- 
arations of  all  degrees  of  value,  among  them  some  of  exceeding 
merit  and  largely  used,  others  of  doubtful  worth,  some  worth- 
less if  not  dangerous.  Many  of  the  preparations  of  this  class 
contain  cocain  as  the  anaesthetic,  and  frequently  a  little  nitro- 
glycerin as  a  cardiac  stimulant  to  counteract  the  depressant 
effect  of  the  alkaloid.  Carbolic  acid  and  oil  of  cloves  are  also 
frequently  used. 

Many  of  the  constituents  of  this  class  of  anaesthetics  may 
readily  be  identified  by  the  processes  of  microchemical  analysis 
to  which  previous  reference  has  been  made;  others  may  be  de- 
tected by  special  tests,  some  of  which  are  given  under  the  various 
substances  in  the  following  list.  This  list  has  been  extended  to 
include  a  considerable  number  of  preparations  of  common 
occurrence. 

Acoin,   a  synthetic  compound  (chemically  diparanisyl-mono- 

X(NC6H40CH3)2\  \ 

phenetyl-guanidine   hydrochlorid,    C  HCl  j  sol- 

\(NC6H40C2H5)/  / 

uble  in  both  alcohol  and  water.     Strongly  antiseptic  and  a 
valuable    anaesthetic,    especially    in    conjunction    with    cocain. 

164 


LOCAL  ANESTHETICS  165 

Acoin  should  be  used  only  in  solution  and  this  should  be  kept 
in  a  dark  place. 

Adrenalin,  a  valuable  haemostatic  and  frequently  used  in  con- 
junction with  dental  anaesthetics,  is  the  active  principle  of  the 
suprarenal  gland  -or  capsule.  It  occurs  as  very  small  white 
crystals  which  are  not  very  stable  and  only  slightly  soluble 
in  water,  hence  the  article  is  usually  sold  in  solution  with  sodium 
chlorid,  according  to  the  following  formula  taken  from  a  com- 
mercial sample: 

Adrenalin  chlorid,  i  part;  normal  sodium  chlorid  solution 
(with  0.5%  chloretone,)  1000  parts.  This  solution  is  usually 
diluted  with  the  normal  (0.6%)  salt  solution.  According  to  the 
Druggists'  Circular,  preparations  similar  to  the  above  are  also 
marketed  under  the  names  of  adrenol,  adnephrin,  hemostatin, 
supraredalin,  etc. 

Alypin.  —  Benzoyl  -  dimethylamino  -  methyl  -  dimethylami no- 
butane  hydrochlorid,  white  crystaUine,  hygroscopic,  melts  at 
169°  C.     Soluble  in  water  and  alcohol. 

Alypin  can  be  steriHzed  without  decomposition,  is  not  half 
so  poisonous  as  cocain  and  is  cheaper.  Is  used  in  2%  solution. 
Solution  should  be  freshly  made  and  prolonged  boiUng  avoided. 
Sometimes  used  with  adrenaHn.     (Cosmos,  1908,  p.  889). 

Alypin  nitrate  occurs  as  a  white,  crystalHne  powder  melting 
at  159°  C,  readily  soluble  in  ether.  Mfrs.:  Farbenfabriken  of 
Elberfeld,  Elberfeld  (Germany)  and  New  York.  (Mod.  Mat. 
Med.,  page  21). 

Ammonium  bifluorid  is  strongly  recommended  as  a  solvent 
for  tartar  by  Dr.  Joseph  Head  of  Philadelphia.  In  Items  of 
Interest,  Vol.  31,  page  174,  Dr.  Head  gives  the  following  method 
for  its  preparation.  Hydrofluoric  acid  is  neutrahzed  with  am- 
monium carbonate,  the  solution  filtered  and  evaporated  to  half 
its  bulk,  the  original  volume  restored  by  adding  more  hydro- 
fluoric acid  and  then  the  resulting  mixture  is  again  concentrated 
to  half  its  volume  by  evaporation. 


l66  MICROCHEMICAL  ANALYSIS 

Anesthol,  or  Anaesthol,  is  a  mixture  of  ethyl  chlorid  and 
methyl  chlorid,  used  as  a  local  dental  anaesthetic.  The  name  is 
also  applied  to  a  general  anaesthetic  given  by  inhalation  and  con- 
sisting of  a  mixture  of  ethyl  chlorid  17  parts,  chloroform  35.89 
parts,  and  ether  47.1  parts. 

Anaestheaine,  a  local  anaesthetic,  contains  5  grains  of  stovain 
to  the  fluid  ounce. 

Argyrol,  a  protein  compound  of  silver,  occurs  as  dark 
brown  crystals  containing  30%  of  Ag.  It  is  easily  soluble  in 
water.  It  does  not  precipitate  chlorin  nor  coagulate  albumin, 
and  is  recommended  for  use  in  place  of  ordinary  silver 
nitrate. 

Aristol  is  given  by  the  U.  S.  D.  as  a  S3nion3an  for  dithymol- 
diiodid  which  contains  45%  of  iodin  and  is  used  as  an  anti- 
septic similarly  to  iodoform. 

Atropin,  an  alkaloid  obtained  from  belladonna,  usually  used 
combined  with  sulphuric  acid,  (Ci7H23N03)2H2S04;  the  alkaloid 
is  only  sparingly  soluble  in  water  but  the  sulphate  is  easily  solu- 
ble, dissolving  in  about  one  half  part  of  water  at  ordinary 
temperature.  A  1%  solution  is  said  to  produce  complete  insen- 
sibility of  the  nerves  in  cases  in  which  an  artificial  tooth  is 
inserted  in  a  living  root.     (U.  S.  D.,  page  249.) 

Tests.  —  Atropin  may  be  separated  from  a  local  anaesthetic 
by  first  rendering  the  mixture  alkaline  with  ammonia  and 
shaking  with  chloroform.  Upon  evaporation  of  the  chloro- 
form solution  on  a  watch-glass  the  resulting  residue  may  be 
tested  by  adding  a  drop  or  two  of  sulphuric  acid  and  a  trace  of 
potassium  bichromate  and  a  little  water.  The  odor  of  bitter 
almonds  is  produced.  A  more  conclusive  test  is  to  convert  the 
alkaloid,  which  has  been  dissolved  by  the  chloroform,  into  a  salt 
by  the  addition  of  a  few  drops  of  acetic  acid,  evaporating  to 
complete  dryness,  taking  up  in  a  few  drops  of  distilled  water 
and  placing  one  or  two  drops  of  this  solution  in  the  eye  of  a 
cat,  when,  if  atropin  is  present,  a  dilation  of  the  pupil  occurs 


LOCAL    ANESTHETICS  1 67 

in  from  fifteen  minutes  to  an  hour  and  a  half,  according  to 
amount  present. 

Borax.  —  Sodium  tetraborate,  Na2B407,  is  used  in  antiseptic 
solutions  and  may  be  detected  as  follows:  evaporate  a  little  of 
the  solution  to  dryness,  add  a  little  HCl,  evaporate  to  dryness 
a  second  time,  then  add  a  very  dilute  HCl  solution  containing 
tincture  turmeric.  Upon  drying  this  mixture  a  beautiful  pink 
color  appears.  If  much  organic  matter  is  present  it  may  be 
burned  off  in  the  Bunsen  flame  before  the  addition  of  any  acid. 

Carbolic  Acid.  —  See  Phenol. 

Chloral  Hydrate,  CCI3CHO.H2O,  a  crystalHne  solid  com- 
posed of  trichloraldehyd  or  chloral  with  one  molecule  of  water, 
(U.  S.  P.)  easily  soluble  in  water,  may  become  with  alcohol  a 
chloral  alcoholate  comparatively  insoluble  in  water. 

Tests.  —  Chloral  may  be  detected  by  adding  to  the  sus- 
pected mixture  a  few  cubic  centimeters  of  fairly  strong  alco- 
holic solution  of  KOH  or  NaOH  with  one  drop  of  aniline  oil  and 
heating,  when  isobenzonitril  is  produced,  which  has  a  peculiarly 
disagreeable  and  characteristic  odor.  This  test  is  also  given 
by  chloroform,  which  is  produced  by  heating  chloral  hydrate 
with  caustic  alkali.  If  more  than  traces  of  chloral  are  present 
this  latter  reaction  may  be  a  sufficient  test. 

Chloretone,  CCl3COH(CH3)2,  is  the  commercial  name  of 
acetone-chloroform  or  tertiary  trichlorbutyl  alcohol.  Made 
from  chloroform,  acetone,  and  an  alkali,  and  occurs  as  small 
white  crystals,  with  taste  and  odor  like  camphor.  It  is 
dissolved  by  alcohol  and  glycerin  and  to  a  slight  extent  by 
water. 

Tests.  —  A  convenient  microchemical  test  for  chloretone 
devised  by  Dr.  Niles,  Harvard  Dental  School,  '06,  consists 
simply  of  treatment  with  a  solution  of  hypochlorite  of  sodium. 
A  precipitate  is  at  once  formed  of  a  coarsely  branching  character 
which  thus  far  seems  to  be  characteristic  of  chloretone  solutions 
(Plate  IV,  Fig.  4). 


-l68  MICROCHEMICAL  ANALYSIS 

Chloroform,  trichlormethane,  CHCI3,  prepared  by  action  of 
chlorinated  lime  on  acetone.  Chloroform  is  a  heavy  colorless 
-Hquid  with  a  specific  gravity  of  1.490  at  15°  C.  Is  very 
volatile  and  used  as  a  solvent  for  gutta-percha,  caoutchouc, 
many  vegetable  balsams,  camphor,  iodin,  bromin,  and  chlorin; 
it  also  dissolves  sulphur  and  phosphorus  to  a  limited 
extent. 

Tests.  —  It  may  be  detected  by  its  odor,  when  heated,  or  by 
the  isobenzonitril  test  to  which  reference  has  been  made  under 
chloral  hydrate. 

Cocain  is  the  alkaloid  obtained  from  erythroxylon  coca. 
The  hydrochlorate,  C17H21NO4HCI,  is  the  salt  most  usually 
employed.  This  is  easily  soluble  in  water  and  very  largely 
used  as  a  dental  anaesthetic  in  a  i  or  2  per  cent  solution. 

Tests.  —  Cocain  solutions  respond  to  the  usual  alkaloidal 
reagents.  With  1%  solution  potassium  permanganate  gives 
pink  plates  in  form  resembling  cholesterin  (Plate  III,  Fig.  4) 
in  form  but  not  in  color. 

Dilute  cocain  solution  with  picric  acid  gives  a  yellow  pre- 
cipitate which  becomes  crystalline  on  standing.  Quite  char- 
acteristic crystals  also  may  be  obtained  from  dilute  cocain 
solutions  and  stannous  chlorid  in  the  presence  of  free  HCl 
(Plate  IV,  Fig.  3). 

Creosote.  —  A  mixture  of  phenols  derived  from  the  destruc- 
tive distillation  of  wood  tar.  It  is  a  heavy  oily  liquid  acting 
when  pure  as  an  escharotic.  It  is  analogous  in  many  respects 
to  carboHc  acid  and  may  be  used  for  similar  purposes.  To 
distinguish  between  creosote  and  carbolic  acid,  boil  with  nitric 
acid  until  red  fumes  are  no  longer  given  off.  Carbolic  acid  will 
give  yellow  crystalline  deposit;  creosote  will  not.  An  alco- 
hoUc  solution  of  creosote  is  colored  emerald  green  by  an  alcoholic 
solution  of  ferric  chlorid.     Phenol  is  colored  blue. 

Cresol  is  the  next  higher  homologue  to  phenol,  having  a 
formula  C6H4CH3OH,  boihng  at   198°  C.     It  is  largely  used, 


LOCAL  ANESTHETICS  169 

usually  together  with  allied  compounds  from  coal-tar,  as  anti- 
septic and  disinfectant  solutions. 

Ektogan.  —  Peroxid  of  zinc,  Zn02,  designed  for  external 
use  (London,  July  9,  1904). 

Ethyl  Chlorid  monochlorethane,  C2H5CI.  This  is  a  gaseous 
substance  at  ordinary  temperature,  but  when  used  as  a  dental 
anaesthetic  it  is  compressed  to  a  colorless  liquid  which  has  a 
specific  gravity  of  0.918  at  8°  C,  is  highly  inflammable  and  usu- 
ally sold  in  sealed  glass  tubes  of  from  10  to  30  grams  each. 

P-Eucain  is  the  hydrochlorate  of  benzoylvinyldiacetone- 
alkamine,  and  occurs  as  a  white,  neutral  powder,  soluble  in 
about  30  parts  of  cold  water.  It  is  used  like  cocain  as  a  local 
anaesthetic,  and  is  claimed  to  be  less  toxic,  and  steriHzable  by 
boiling  without  danger  of  decomposition.  It  is  usually  applied 
in  from  i  to  5  per  cent  solutions,  which  are  conveniently  prepared 
in  a  test-tube  with  boiling  water.  It  is  also  marketed  in  the 
form  of  i|-  and  5-grain  tablets.     (Druggists'  Circular.) 

Eucain  Lactate.  —  "  Eucain  lactate  is  used  in  2  to  5  per  cent 
solution  as  a  local  anaesthetic  in  ophthalmic  and  dental  prac- 
tice and  in  10  to  15  per  cent  solution  when  used  in  the  nose  or 
ear. "     (Review  of  American  Chemical  Research,  page  97,  1905). 

Eudrenin  is  a  local  anaesthetic  marketed  in  capsules  of 
0.5  c.c.  containing  1/12  grain  of  eucaine  and  1/4000  grain  of 
adrenaHn  hydrochlorid.  It  is  used  as  a  local  anaesthetic,  chiefly 
in  dentistry.  The  contents  of  one  or  two  capsules,  according 
to  the  number  of  teeth  to  be  extracted,  are  injected  into  the 
gums  ten  minutes  before  extraction.  Mfrs. :  Parke,  Davis  & 
Co.,  Detroit,  Mich.     (Mod.  Mat.  Med.,  page  147.) 

Eugenol,  C10H12O2,  synthetical  oil  of  cloves.  Eugenol  is  mis- 
cible  with  alcohol  in  all  proportions.  Exposure  to  air  thickens 
and  darkens  it. .  Should  be  kept  in  well-stoppered  amber-colored 
bottles  (U.  S.  D.). 

Europhen  —  recommended  by  Dr.  J.  P.  Buckley  as  a  sub- 
stitute for  iodoform  (Dental  Review,  Vol.  21,  page  1284). 


lyo  MICROCHEMICAL   ANALYSIS 

Di-iso-butyl-cresol  is  described  as  a  bulky  yellow  powder  of  faint 
saffron  odor  and  containing  28%  of  iodin.  (Mod.  Mat.  Med., 
page  152.) 

Formalin,  Formol,  Formin,  etc.,  are  commercial  names 
for  a  40%  aqueous  solution  of  formaldehyd,  HCHO,  prepared 
by  the  partial  oxidation  of  methyl  alcohol.  Formalin  is  a 
powerful  disinfectant  very  generally  used.  (For  test  see  page 
201,  Exp.  62.) 

Glycerol  is  a  triatomic  alcohol,  C3H5(OH)3,  a  colorless  liquid 
of  syrupy  consistence  and  sweetish  taste,  specific  gravity  1.250 
at  15°  C.     It  is  easily  soluble  in  either  water  or  alcohol. 

Tests.  —  Upon  heating  strongly  it  is  decomposed,  giving 
off  odor  of  acrolein,  which  is  usually  sufficient  for  its  identi- 
fication. A  further  test  may  be  made  by  moistening  a  borax 
bead  on  a  platinum  wire  with  the  suspected  solution  (after  con- 
centration) and  holding  in  a  non-luminous  flame,  to  which  it 
will  give  a  deep-green  color  which  does  not  persist.  Glycerol 
when  present  is  apt  to  interfere  with  characteristic  crystalliza- 
tion of  many  precipitates. 

Gram's  Solution,  Kuhne's  modification,  contains  2  grams 
of  iodin,  and  4  grams  potassium  iodid  in  100  c.c.  of  water. 

Gutta-percha.  The  name  signifies  scraps  of  gum.  It  is  ob- 
tained as  a  milky  exudate  from  a  number  of  tropical  trees.  It 
is  soluble  in  ether,  chloroform,  carbon  disulphid,  toluene  and, 
petroleum  ether.  It  may  be  freed  from  impurities  by  shaking 
the  solution  with  calcium  sulphate,  which  will  mechanically  carry 
coloring  matter  and  other  impurities  with  it  as  it  slowly  settles 
out  from  the  mixture.     It  is  not  soluble  in  alcohol  or  in  water. 

Heroin  is  a  diacetic  ester  of  morphin.  It  is  usually  ob- 
tained as  the  hydrochlorid  and  occurs  as  a  white  powder,  solu- 
ble in  two  parts  of  water.  Its  action  is  similar  to  that  of  morphin ; 
it  answers  to  the  usual  tests  for  morphin,  but  may  be  distinguished 
from  it  by  the  fact  that  it  will  yield  acetic  ether  upon  heating 
with  alcohol  and  sulphuric  acid. 


LOCAL   ANESTHETICS  171 

Hopogan  (also  known  as  biogen)  is  a  peroxid  of  magnesium, 
Mg02,  recommended  as  a  non-poisonous  and  non-astringent 
intestinal  germicide. 

Hydrogen  Peroxid,  or  dioxid,  H2O2,  is,  when  pure,  a  syrupy 
liquid  without  odor  or  color.  It  is  sold  under  various  trade 
names  in  aqueous  solution  containing  about  3%  and  yielding 
upon  decomposition  about  10  volumes  of  oxygen  gas.  It  is 
used  also  as  an  escharotic  in  etherial  solutions  containing  25  to 
50  per  cent  H2O2.  Peroxid  solutions  may  be  concentrated  by 
heat  without  decomposition  if  kept  perfectly  free  from  dirt  or 
traces  of  organic  matter.  It  is  readily  prepared  by  treatment  of 
metallic  peroxids,  as  Ba02  with  dilute  acids. 

Ba02  +  H2SO4  =  BaS04  +  H2O2 
or  Ba02  +  H2O  -j-  CO2  =  BaCOs  +  H2O2. 

This  latter  reaction  has  the  advantage  of  producing  an  insolu- 
ble barium  compound  and  at  the  same  time  introducing  no 
objectionable  acid.  The  peroxids  of  sodium,  calcium,  magne- 
sium, and  zinc  may  also  be  used;  Zn02,  however,  is  compara- 
tively expensive  and  used  in  powder  form  as  an  antiseptic 
dressing  rather  than  as  a  source  of  H2O2.  Na202  is  valuable  as 
a  bleaching  agent,  because  for  this  purpose  an  alkaHne  solution 
is  required  and  the  solution  of  Na202  in  water  produces  both 
alkali  and  H2O2  according  to  the  following  reaction: 

Na202  +  2  H2O  =  2  NaOH  +  H2O2. 

Sodium  perborate  (page  175),  also  sold  as  euzone,  is  a  powder 
advertised  to  produce  H2O2  in  water.  Commercial  H2O2  solu- 
tions are  usually  acid  in  reaction,  as  such  solutions  are  more 
stable  than  if  neutral  or  alkaline. 

LugoPs  Caustic  lodin  is  made  of  iodin  and  potassium 
iodid,  I  part  of  each  dissolved  in  2  parts  of  water. 

Lugol's  Iodin  Solution  contains  5  grams  of  odin  and  10 
grams  of  potassium  iodid  dissolved  in  sufficient  water  to  make 
100  grams. 


172  MICROCHEMICAL  ANALYSIS 

Menthol  is  the  stearopten  obtained  from  the  oil  of  pepper- 
mint. It  is  a  volatile  crystalline  substance  having  a  formula 
C6H9OHCH3C3H7.  Menthol  is  but  slightly  soluble  in  water 
but  freely  soluble  in  alcohol,  ether,  chloroform,  or  glacial  acetic 
acid.  The  presence  of  menthol  may  usually  be  detected  by 
its  odor.  If  the  odor  should  be  suggestive  but  not  distinctive 
it  is  well  to  place  a  little  of  the  substance  on  a  filter-paper,  rub 
it  between  the  thumb  and  finger,  thereby  obtaining  a  ' '  fractional 
evaporation,"  when  the  more  easily  volatile  substance  will  pass 
off  first,  thus  producing  a  partial  separation  of  substances. 

Mercuric  Chlorid,  corrosive  sublimate,  HgCl2,  is  soluble  in 
about  16  parts  of  water  and  3  parts  of  alcohol.  It  is  a  power- 
ful antiseptic,  in  aqueous  solution  i/iooo  to  1/5000,  but  should 
never  be  used  in  mouth-washes. 

Tests.  —  A  drop  of  the  suspected  solution  with  a  trace  of 
potassium  iodid  will  give  a  red  precipitate  of  mercuric  iodid 
soluble  in  excess  of  either  reagent.  With  lime-water  or  fixed 
alkaline  hydroxids  a  black  precipitate  is  produced.  A  drop  of 
mercurial  solution  placed  on  a  bright  copper  plate  will  leave 
a  tarnished  spot  due  to  the  reduction  of  the  mercuric  salt  and 
subsequent  amalgamation  of  the  metal. 

Methethyl.  —  Ethyl  chlorid  mixed  with  a  little  methyl  chlorid 
and  chloroform  is  said  to  be  the  composition  of  a  local  anaes- 
thetic sold  under  the  name  of  methethyl  (U.  S.  D.). 

Methyl  Chlorid,  CH3CI,  is  a  colorless  gas  which  condenses  to 
a  liquid  at  23°  C.  Methyl  chlorid  is  easily  soluble  in  alcohol, 
somewhat  in  water,  and  is  used  in  a  similar  manner  to  ethyl 
chlorid. 

Morphin,  C17H19NO3,  alkaloid  from  opium.  Solutions  for 
use  are  made  from  the  sulphate,  hydrochlorate,  or  acetate.  The 
alkaloid  itself  is  insoluble  in  water ;  its  salts  are  easily  soluble. 

Morphin  may  be  separated  from  solutions  containing  it  by 
making  the  solution  alkalin  with  ammonia,  and  shaking  out 
the    precipitated    alkaloid    with    warm    amyl    alcohol.     Upon 


LOCAL  ANESTHETICS  1 73 

evaporation  of  the  alcohol  the  residue  may  be  tested  with 
Frohde's  reagent  (sodium  molybdate,  1%,  in  strong  sulphuric 
acid).  The  color  obtained  should  be  a  violet,  changing  usually 
to  brown;  a  pure  blue  color  is  not  distinctive  for  morphin.  If 
the  morphin  solution  is  of  sufficient  strength  the  addition  of  am- 
monia will  produce  minute  crystals  of  the  alkaloid  as  shown  on 
Plate  III,  Fig.  6.  Dental  anaesthetics  containing  morphin  will 
give  precipitates  with  the  usual  alkaloidal  reagents.  Marme's 
reagent  (Cdl2)  gives  crystals  represented  on  Plate  IV,  Fig.  i. 

Nirvanin,  hydrochlorid  of  diethyl-glycocoll-/>-amino-o-oxy- 
benzoic-methylester,  of  the  formula 

(CH2N)    =    (C2H5)2HC1 

(CO.NH.C6H4(OH)COOCH3. 

White  prisms  soluble  in  water  and  in  alcohol,  melt  at  185°  C, 
violet  reaction  with  ferric  chlorid. 

Nitroglycerin,  C3H5(N03)3,  is  used  as  a  cardiac  stimulant 
in  alcoholic  solution,  the  U.  S.  P.  Spiritus  Glonoini,  containing 
1%  by  weight  of  the  substance. 

Novocain,  discovered  by  Uhlfelder  and  Einhorn,  is  a  hydro- 
chlorid /^-aminobenzoyl-diethylamino-ethanol.  It  occurs  as  thin 
colorless  needles;  melts  at  156°  C,  soluble  in  i  part  Il20  and 
30  parts  alcohol.  It  is  seven  times  less  toxic  than  cocain,  and 
three  times  less  toxic  than  stovain.  It  can  be  sterilized  by 
boiHng,  and  is  used  in  1/2  to  2%  solution  often  with  adrenalin 
i/iooo.     (Mod.  Mat.  Med.,  page  275). 

Novocain,  if  intended  to  represent  a  solution  which  is 
isotonic  with  the  blood  corpuscles,  must  be  dissolved  in  a  0.92 
per  cent  sodium  chlorid  solution.  (Dental  Cosmos,  19 10,  page 
605.) 

Oil  of  Cloves,  oil  of  Gaultheria,  and  other  essential  oils  may 
be  detected  by  the  same  process  of  fractional  evaporation  as 
suggested  for  menthol.     In  testing  for  the  presence  of  any  sub- 


174  MICROCHEMICAL  ANALYSIS 

stance  by  its  odor,  it  is  usually  necessary  to  make  a  comparative 
test  on  known  samples  using  the  same  methods. 

Orthoform,  C6H30H(NH2)COOCH3,  methylparaamino- 
metaoxybenzoate,  used  as  an  anaesthetic  and  antiseptic,  is 
without  odor,  color,  or  taste,  is  slightly  soluble  in  water  and 
easily  soluble  in  alcohol  or  ether. 

Phenol.  —  CarboHc  Acid.  CeHgOH,  obtained  from  the  de- 
structive distillation  of  coal-tar.  A  light  oily  hquid  of  specific 
gravity  of  0.94-0.99.  Carbolic  acid  is  usually  obtained  as  a 
white  crystalline  mass  soluble  in  20  parts  of  water.  The  pure 
acid  turns  pink  with  age,  but  does  not  suffer  deterioration  on 
account  of  this  change  of  color.  The  addition  of  from  5  to  8 
per  cent  of  water  will  cause  liquefaction  of  the  crystals  and  the 
preparation  becomes  permanently  Hquid.  It  is  easily  soluble 
in  glycerol  and  strong  solutions  may  thus  be  prepared.  Car- 
boHc acid  is  sometimes  added  to  local  anaesthetics  with  the  in- 
tent of  rendering  the  solution  sterile,  but  as  shown  by  Dr. 
Endelman  (Dental  Cosmos  Vol.  45,  page  44)  it  would  be  neces- 
sary, in  order  to  prevent  the  development  of  micro-organisms,  to 
add  the  acid  in  proportion  that  would  render  the  solution  unfit 
for  hypodermic  purposes. 

Tests.  —  Phenol  may  be  detected  in  the  majority  of  prepara- 
tions by  the  addition  of  bromin-water,  which  gives  white  crys- 
tals of  tribromphenol  (see  Plate  III,  Fig.  5). 

Phenol  Compound  —  Dr.  Buckley's  formula  for  treatment  of 
root  canals — ^ menthol  1.3  grams,  thymol  2.6  grams  and  phenol 
12  c.c. 

Potassium  Hydroxid,  KOH,  gives  an  alkaHne  reaction  to 
Htmus  paper  and  may  be  detected  by  the  ordinary  methods  of 
inorganic  analysis. 

Rhigolene  is  a  Hght  inflammable  Hquid  obtained  from 
petroleum,  boiHng  at  about  18°  C,  used  as  a  spray  for  the 
production  of  low  temperature,  similarly  to  methyl  or  ethyl 
chlorid.     It  is  readily  inflammable,  and  the  vapor,  mixed  with 


LOCAL  ANESTHETICS  175 

certain  proportions  of  air  is  explosive.     It  should  be  kept  in  a 
cool  place. 

Saccharin  —  the  commercial  name  of  benzosulphinid,  a 
derivative  of  toluene  —  is  a  white  crystalline  powder  300  times 
sweeter  than  cane  sugar  and  is  used  in  mouth- washes,  tooth- 
paste, etc.,  as  a  flavor  and  an  antiseptic. 

Silver  Nitrate,  AgNOs,  crystallizes  in  colorless  plates 
without  water  of  crystallization;  used  as  an  antiseptic,  dis- 
infectant, or  escharotic.  It  is  freely  soluble  in  water  and  may 
be  detected  by  the  ordinary  methods  of  qualitative  analysis 
(page  19). 

Sodium  Chlorid,  NaCl,  is  a  constituent  of  many  prepa- 
rations designed  to  be  used  hypodermically.  Experience  has 
proved  the  value  of  such  addition;  perhaps  the  reason  for  its 
desirability  is  given  by  Dr.  G.  Mahe,  of  Paris,  in  the  Dental 
Cosmos  for  September,  1903,  in  the  statement  that  sodium 
chlorid  added  in  excess  to  a  toxic  substance  diminishes  its 
toxicity  by  one  half,  and  this  has  been  demonstrated  particu- 
larly with  cocain. 

Sodium  Perborate,  a  powder  said  to  have  the  composition 
NaB03.4  H2O,  which  will  furnish  10%  of  available  oxygen  and 
produce  H2O2  with  water;  very  stable  and  recommended  as  a 
bleach-powder. 

Sodium  perborate  may  be  made  *  by  thoroughly  mixing 
78  grams  Na20  and  248  grams  of  crystallized  H3BO3  and  stirring 
the  mixture  gradually  into  2  liters  of  cold  H2O.  The  sodium 
perborate,  Na2B408  -|-  10  H2O,  is  formed  spontaneously  and 
settles  out  from  the  solution  as  a  white  crystalHne  powder. 
Its  solubiHty  is  increased  by  addition  of  weak  organic  acids, 
citric  or  tartaric. 

Sodium  Peroxid,  Na202.  —  A  white  powder  easily  soluble  in 
water,  usually  with  evolution  of  more  or  less  oxygen  and  forma- 
tion of  hydrogen  dioxid. 

*  Dental  Cosmos,  Nov.,  1905,  page  1381. 


176  MICROCHEMICAL  ANALYSIS 

Somnoform.  —  A  general  aricesthetic  administered  in  manner 
similar  to  chloroform;  introduced  by  Dr.  Rolland,  of  Bordeaux; 
consists  of  60%  ethyl  chlorid,  35%  ethyl  bromid,  and  5% 
methyl  bromid.     (  Dental  Cosmos,  Vol.  XL VII,  page  236.) 

Stovain.  — Benzoylethyldimethyl-aminopropanol  hydrochlo- 
rid,  C14H21O2N.HCI,  closely  related  to  alypin,  small  shining 
scales  freely  soluble  in  alcohol  or  water.  Incompatible  with 
alkaUes  and  all  alkaloidal  reagents.  Can  be  sterilized  by  boil- 
ing.    (Mod.  Mat.  Med.,  2nd  edition.) 

It  melts  at  175°  C,  is  very  soluble  in  H2O,  and  gives  reaction 
similar  to  cocain,  which  is  also  a  benzoyl  derivative.  (U.  S.  D., 
page  1 66 1.) 

It  is  less  powerful  than  cocain  and  physiologically  incom- 
patible with  adrenalin.     (Dental  Cosmos,  1905,  page  146.) 

Tannic  Acid,  or  tannin,  sometimes  called  gallotannic  acid, 
is  an  astringent  organic  acid  obtained  from  nutgalls.  It  may 
be  obtained  as  crystals  carrying  2  molecules  of  water, 
HC14H9O9  2  H2O.  Tannic  acid  is  a  white  or  slightly  yellowish 
powder  soluble  in  about  one  part  of  water  or  0.6  part  alcohol. 
It  is  used  as  an  alkaloidal  precipitate,  also  in  astringent  washes. 
It  may  be  detected  by  the  addition  of  ferric  solutions  which 
form  with  it  a  black  tannate  of  iron  of  the  nature  of  ink. 

Thymol,  C6H3(CH3)(OH)(C3H7)  1:3:4:  a  phenol,  occurring 
in  volatile  oils  of  thjnnus  vulgaris  (Linne).  Melts  at  44°  C; 
sparingly  soluble  in  water,  easily  in  alcohol  and  ether. 

Tests.  —  It  may  usually  be  detected  by  its  odor  or  by  dis- 
solving a  small  crystal  in  i  c.c.  of  glacial  acetic  acid,  when  if 
6  drops  of  sulphuric  acid  and  i  drop  of  nitric  acid  be  added, 
the  liquid  will  assume  a  deep  bluish-green  color.     (U.S.D.) 

Thymophen,  a  mixture  of  equal  parts  of  thymol  and 
phenol. 

Trichloracetic  Acid  occurs  as  deliquescent  crystals,  readily 
soluble  in  water.  Distils  at  195°  C.  and  is  a  powerful  caustic. 
Dilute  solutions  are  recommended  for  treatment  of  pyorrhoea. 


LOCAL  ANESTHETICS 


177 


Tropa-cocain  is  an  alkaloid  originally  isolated  by  Giesel 
from  the  leaves  of  the  small-leaved  coca-plant  of  Java  and  intro- 
duced by  Arthur  P.  Chadbourne,  Harvard  Medical  School. 
Used  hypodermically  in  normal  salt  solution.  It  is  probably 
superior  to  cocain,  but  rather  more  expensive.  It  is  obtained 
as  an  oil  which,  when  quite  dry,  solidifies  in  radiating  crystals, 
melting  at  49°  C.     It  is  easily  soluble  in  alcohol. 

Laboratory  Exercises  XLVII  to  XLIX. 
A  number  of  commercial  mouth-washes  and  local  ansesthetics 
will  be  given  to  the  class  for  identification,  the  object  being  to 
familiarize  the  student  with  the  more  easily  made  tests  for  the 
principal  ingredients  of  these  preparations.  Complete  analysis 
will  rarely  be  attempted.  The  following  table,  taken  from  the 
Druggist's  Circular  of  June,  1910,  may  be  helpful. 


DIFFERENTIATION 

OF   COCAIN  AND   ITS   SUBSTITUTES. 

lodin  potassium 
iodid. 

Bromin  water. 

Sodium  hydroxid. 

Potassium  per- 
manganate. 

Eucain  —  a. 

Yellow-maroon 

Yellow  precipitate. 

White  precipitate. 

Violet  precipitate. 

precipitate, 

soluble  on  heat- 

insoluble in  ex- 

blackening 

soluble  on 

ing. 

cess  and  on  boil- 

quickly. 

boiling. 

ing. 

Eucain  —  b. 

Deep-red  pre- 

Yellow precipitate. 

White  precipitate, 

No  precipitate 

cipitate,  solu- 

slightly soluble 

insoluble  in  ex- 

immediately; 

ble  on  boiling. 

on  heating,  re- 

cess  and  on 

color  persists 

precipitated 

boiling. 

for  a  day. 

white  on  boiling. 

Cocain 

Yellow-maroon 

Yellow  precipitate. 

White  precipitate. 

Violet  precipitate, 

precipitate. 

soluble  on  heat- 

insoluble in  ex- 

color persists 

soluble  on 

ing. 

cess  and  on 

for  one  hour. 

boiling. 

boiling. 

then  deposits 
MnOo. 

Novocain 

Deep-red  pre- 

Yellow precipitate. 

White  precipitate. 

Violet  precipitate. 

cipitate,  solu- 

soluble on  heat- 

insoluble in  ex- 

blackening 

ble  on  boiling. 

ing. 

cess  and  on  boil- 

quickly. 

Stovain 

Deep-red  pre- 

Yellow precipitate. 

ing. 
White  precipitate. 

Violet  precipitate, 

cipitate,  solu- 

soluble on  heat- 

insoluble in  ex- 

blackening al- 

ble on  boiling. 

ing. 

cess;  aromatic 
odor  on  boiling. 

most  immedi- 
ately. 

Nirvanin 

Deep-red  pre- 

Yellow precipitate. 

Precipitate  very 

Precipitate,  first 

cipitate,  solu- 

soluble on  heat- 

soluble in  excess 

maroon,  then 

ble  on  boiling. 

ing,  but  the 
liquid  becomes 
red  and  gives  an 
agreeable  fruity 
odor. 

of  the  reagent. 

brown. 

Alypin 

Yellow-maroon 

Yellow  precipitate. 

White  precipitate. 

Bluish-violet  pre- 

precipitate, in- 

soluble on  gentle 

insoluble  in  ex- 

cipitate, slowly 

soluble  on 

heating. 

cess  and  on  boil- 

blackening. 

boiling;  orange 

ing. 

red  deposit. 

CHAPTER  XX. 
TEETH  AND   TARTAR. 

The  chemical  examination  of  teeth  and  tartar,  while  coming 
more  properly  under  the  head  of  physiological  chemistry,  will 
be  considered  in  part  in  this  place,  as  the  tests  made,  especially 
on  tartar,  are  practically  all  microchemical.  The  composition 
of  the  cement  is  practically  that  of  true  bone,  the  dentine  and 
enamel  differing  principally  in  the  proportion  of  organic  matter 
which  they  contain.  In  all  of  these  the  presence  of  lime,  phos- 
phoric acid,  carbonic  acid,  and  traces  of  magnesium  and  calcium 
fluorid  may  be  demonstrated.  The  tartar  contains  a  greater 
proportion  of  carbonic  acid,  less  calcium  phosphate,  and  much 
less  organic  matter  than  the  teeth,  taken  as  a  whole,  or  than 
dentine,  but  about  the  same  as  enamel.  According  to  Berzelius, 
sodium  chlorid  and  sodium  carbonate  may  also  be  found. 

The  composition  of  the  different  parts  of  the  tooth  sub- 
stance has  been  given  as  follows : 

Marten  ^^^-  CajCPO^)^.  MgHPO^.  CaCO,. 

Dentine 23.2  76.8  70.3  4.3          2.2 

Cement 32.9  67.1  60.7  1.2          2.9 

Enamel 3.1  96.9  90 . 5  traces        2 . 2 

Also  traces  of  magnesium  carbonate,  calcium  sulphate,  fiuorids, 
and  chlorids.  An  increase  in  the  percentage  of  calcium  phos- 
phate of  fluorid  increases  the  hardness  of  the  tooth,  while  an 
increase  of  calcium  carbonate  decreases  the  hardness. 

Potassium  sulphocyanate,  ferric  phosphate,  sulphites,  and 
uric  acid  have  been  found  in  tartar,  as  additional  chemical 
constituents,  while  after  the  solution  of  the  mineral  matter 

178 


TEETH  AND   TARTAR  179 

the  presence  of  epithelium  cells,  mucus,  and  the  leptothrix  may 
be  demonstrated  by  the  microscope. 

According  to  Vergness,  Du  tartre  dentaire,  quoted  by  Gamgee, 
the  tartar  from  incisor  teeth  and  that  from  molars  show  decided 
difference  in  their  content  of  iron  and  calcium  phosphates,  the 
analysis  being  as  follows: 

Tartar  of  Incisors.  Tartar  of  Molars. 

Calcium  phosphate 63.88-62.56  55-  ""62.12 

Calcium  carbonate 8.48-8.12  7.36-8.01 

Phosphate  of  iron 2.72-0.82  12.74-  4.oi 

Silica 0.21-  0.21  0.37-0.38 

Alkaline  salts 0.21-  0.14  0.37-0.31 

Organic  matter 24.99-27-98  24.40-24.01 

Tartar  from  patients  with  pyorrhoea  has  been  found  to 
contain  oxalates  and  urates,  not  necessasily  together,  but  often 
one  or  the  other.  The  deficient  oxidation  and  high  acidity 
usually  occurring  in  such  cases  is  conducive  to  the  production 
of  large  amounts  of  oxaHc  or  uric  acids  (most  generally  the 
latter)  whether  these  substances  have  etiological  relations  to 
pyorrhoea  or  not. 

Lactic  and  other  organic  acids  have  been  found  in  minute 
quantities  in  tartar,  but  these  as  well  as  the  qualitative  tests  for 
urates  will  be  considered  more  in  detail  under  the  Chemistry 

of  Saliva. 

Analysis  of  Teeth  and  Tartar. 

The  substance  for  analysis  should  be  reduced  to  a  moder- 
ately fine  powder  by  crushing  in  a  mortar  and  a  fair  sample 
of  the  whole  taken  for  each  test. 

Moisture  may  be  detected  by  the  closed-tube  test  (page  99) 
and  may  be  determined  by  accurately  weighing  out  i  gram 
of  the  substance  in  a  counterpoised  platinum  dish  or  crucible 
and  drying  at  100°  C.  to  constant  weight. 

Inorganic  Matter  may  be  determined  by  careful  ignition 
of  dried  substance;  raise  the  temperature  slowly  till  full  red  heat 
is  reached;  cool  in  a  desiccator  and  weigh. 

Organic  Matter  may  be  ascertained  by  difference. 


l8o  MICROCHEMICAL  ANALYSIS 

Lactates  and  other  organic  acids  may  be  detected  by  careful 
crystallization  and  examination  with  the  micropolariscope. 

The  several  inorganic  constituents  may  be  demonstrated 
as  follows: 

Phosphoric  Acid.  —  Dissolve  a  little  of  the  powdered  sub- 
stance in  dilute  HNO3 ;  then  to  a  few  drops  of  the  clear  solution 
add  an  excess  of  ammonium  molybdate  in  nitric  acid.  A  yellow 
crystalline  precipitate  of  ammonium  phosphomolybdate  will 
separate.  Avoid  heating  above  60°  C,  as  the  ammonium 
molybdate  may  decompose  and  precipitate  a  yellow  oxid  of 
molybdenum. 

Carbonic  Acid  may  be  detected  by  liberation  of  CO2  and 
passing  the  gas  into  lime-water  as  described  on  page  87  or 
with  closed  tube  and  drop  of  baryta-water,  page  99. 

Chlorin  may  be  detected  in  the  dilute  nitric  acid  solution  by 
the  usual  silver  nitrate  test. 

Calcium  and  Magnesium  may  be  separated  and  identified 
by  the  usual  methods  of  analysis  in  the  presence  of  phosphates. 

Test  for  calcium  and  magnesium  as  follows:  Add  to  the 
HCl  solution  an  excess  of  ammonia;  calcium  phosphate  and 
magnesium  phosphate  are  precipitated,  white.  Filter,  and  to 
the  filtrate  add  ammonium  oxalate;  a  white  precipitate  shows 
Hme,  not  as  phosphate.  Wash  the  precipitate  produced  by 
NH4OH,  dissolve  in  dilute  HCl,  and  add  Fe2Cl6  carefully  till 
a  drop  of  the  solution  gives,  when  mixed  with  a  drop  of  NH4OH, 
a  yellowish  precipitate.  Nearly  neutralize  with  Na2C03  and 
add  BaCOa,  which  precipitates  ferric  phosphate.  Filter,  heat 
the  filtrate,  precipitate  the  barium  with  dilute  sulphuric  acid, 
and  filter  again.  From  the  filtrate  calcium  is  precipitated  as 
white  calcium  oxalate  by  making  it  alkaline  with  NH4OH  and 
adding  (NH4)2C204  as  long  as  a  precipitate  is  formed.  Filter 
and  add  to  the  filtrate  sodium  phosphate,  which  precipitates 
magnesium  as  ammonio-magnesium  phosphate,  white. 

Laboratory  Exercises  No.  L  will  consist  of  the  examina- 
tion by  microchemical  methods  of  one  or  more  samples  of  tartar. 


PART   V. 
ORGANIC   CHEMISTRY. 

CHAPTER  XXI. 
THE  HYDROCARBONS  AND  SUBSTITUTION  PRODUCTS. 

Our  work  up  to  this  point  has  been  confined  to  inorganic 
chemistry  excepting  a  few  microchemical  tests  for  organic 
substances. 

We  are  now  to  consider  briefly  the  organic  compounds  which 
will  serve  as  a  basis  for  the  intelligent  study  of  physiological 
chemistry,  and  also  some  which  are  of  peculiar  interest  in 
dentistry. 

We  shall  touch  but  lightly  on  some  of  the  subdivisions  of  the 
subject  and  take  up  a  little  organic  chemistry  proper,  a  little 
physiological  chemistry,  a  little  pathological  chemistry,  and 
from  it  all  pick  out  such  facts  as  may  help  us  to  a  better  under- 
standing of  the  problems  of  dentistry. 

As  in  many  other  departments  of  science,  absolute  rules  for 
classification  are  impracticable;  yet  we  may  consider  in  a 
general  way  that  the  organic  compounds  are  those  containing 
carbon  as  a  molecular  constituent.  The  old  conception  that  the 
organic  compound  must  have  been  produced  by  a  vital  process 
of  some  sort  (animal  or  vegetable)  is  of  little  value  unless  we 
confine  our  thought  to  substances  found  in  nature  only. 

■  The  compounds  of  carbon  are  practically  innumerable  and 
very  widely  distributed,  constituting  the  great  bulk  (aside  from 
water)  of  all  vegetable  or  animal  substances. 

i8i 


382  ORGANIC  CHEMISTRY 

The  carbon  compounds  contain  the  elements  of  C  and  H, 
and  when  these  two  only  are  present  they  are  hydrocarbons. 
They  more  frequently  contain  C,  H,  and  O,  and  when  the  H 
and  O  are  present  in  the  proportions  in  which  they  occur  in 
water,  the  compound  is  a  carbohydrate  (with  exceptions). 

In  the  chemistry  of  the  animal  body  the  majority  of  sub- 
stances which  we  meet  contain  C,  H,  O,  and  N  and  often  in 
addition  S  or  P.  Many  other  elements,  notably  the  halogens, 
and  often  the  metals,  may  be  found  in  organic  compounds. 

The  question  of  its  composition  is  then  the  first  one  pre- 
senting itself  in  the  consideration  of  an  organic  substance. 

The  analysis  of  organic  bodies  may  be  made  from  two  dis- 
tinct standpoints:  first,  to  determine  the  various  substances 
which  may  be  separated  from  a  given  organized  body,  as  from 
some  part  of  a  plant;  secondly,  to  determine  the  constituent 
elements  of  one  of  the  substances  so  separated. 

As  an  example  of  the  first  sort  of  analysis,  we  may  find  in  a 
potato  a  certain  basic  principle  (alkaloid),  more  or  less  water, 
and  considerable  starch.  These  may  be  called  proximate  prin- 
ciples, and  the  separation  of  them  would  be  proximate  analysis, 
while  the  second  sort  of  analysis  determines  the  composition  of 
the  starch  molecule  and  is  known  as  ultimate  analysis. 

Qualitative  Tests. 

Carbon.  —  The  presence  of  this  element  may  be  shown  by 
the  "carbonization"  obtained  in  the  preliminary  test,  as  given 
on  page  98. 

Hydrogen  shows  itself  by  the  production  of  moisture  in 
these  same  tests. 

Nitrogen  may  or  may  not  be  indicated  by  the  preHminary 
test.  It  may  be  detected  with  certainty  by  either  of  the 
following  methods : 

(a)  Conversion  into  a  cyanogen  compound; 

A  small  piece  of  thoroughly  dried  albumen  together  with 


THE  HYDROCARBONS  AND  SUBSTITUTION   PRODUCTS      183 

a  little  metallic  potassium,  is  placed  in  a  matrass,  such  as  is 
described  on  page  28,  and  heated  to  redness  for  a  few  minutes. 
(Metalhc  sodium  will  work  as  well  in  most  cases.)  An  alkali 
cyanide,  which  may  be  dissolved  in  water  after  breaking  the 
tube,  is  formed,  and  by  addition  of  a  Httle  yellow  ammonium 
sulphid  and  evaporation  to  dryness  on  a  water-bath  will  be 
changed  to  sulphocyanate,  NH4CNS.  If  the  dry  residue  is  taken 
up  with  dilute  HCl,  filtered,  and  tested  with  a  drop  of  ferric 
chlorid  solution,  the  presence  of  the  sulphocyanate  is  at  once 
shown  by  the  red  color  produced. 

{h)  Conversion  into  free  ammonia. 

Almost  any  nitrogenous  substance  may  be  made  to  evolve 
ammonia-gas  by  simply  heating  in  a  test-tube  with  several  times 
its  bulk  of  soda-lime.  Test  for  NH3  by  moistened  red  litmus 
paper  or  by  odor.  (This  test  is  known  as  that  of  Wohler,  also 
of  Will  and  Varrentrap.) 

The  Kjeldahl  or  moist  combustion  process  is  much  employed 
as  a  quantitative  method  but  may  be  used  qualitatively  as 
follows:  The  substance  is  heated  in  an  ignition-tube  with  con- 
centrated sulphuric  acid  till  a  clear  (not  necessarily  color- 
less) solution  is  obtained.  The  mixture  is  cooled,  diluted  with 
water,  an  excess  of  caustic  soda  added,  and  heat  applied  when 
NH3  is  evolved,  which  may  be  detected  by  litmus  paper  or  by 
odor. 

Sulphur  and  Phosphorus  are  first  completely  oxidized 
either  by  fusion  of  the  substance  with  alkali  nitrate  and  car- 
bonate, or  by  treatment  in  the  wet  way  with  fuming  HNO3 
or  mixture  of  KCIO3  and  HCl.  The  resulting  sulphate  or  phos- 
phate is  detected  by  the  usual  qualitative  methods  (page  92). 

A  sulphur  test  may  also  be  made  by  heating  the  substance 
with  a  httle  concentrated  NaOH  in  the  test-tube.  A  httle 
sodium  sulphid,  which  may  be  detected  by  dropping  onto  a 
bright  silver  coin  or  by  testing  with  lead  acetate  solution,  will 
thus  be  formed. 


1 84  ORGANIC   CHEMISTRY 

Halogens.  —  CI,  Br,  and  I  cannot  be  detected  in  organic 
combinations  by  the  ordinary  qualitative  test  with  AgNOs  and 
dilute  NHO3,  but  must  first  be  converted  into  corresponding 
inorganic  haloid  salts.  This  may  be  done  by  heating  the  organic 
substance  strongly  with  pure  lime,  when  calcium  chlorid,  bromid, 
etc.,  which  may  be  dissolved  in  water  and  tested  in  the  usual 
way,  will  be  formed.     (See  pages  90  and  91.) 

A  test  for  chlorin  or  iodin  may  also  be  made  by  heating 
with  copper  oxid  on  a  platinum  wire  in  the  Bunsen  flame,  chlorin 
giving  first  a  blue  then  a  green  color  to  the  flame.  Iodin  gives 
a  green  only  (Beilstein). 

Test  for  presence  of  C,  H,  and  S  in  dried  albumen. 

Test  for  S  by  the  caustic  soda  test. 

Test  for  P  in  casein  precipitated  from  milk. 

Test  a  few  drops  of  chloroform  for  the  presence  of  chlorin. 

The  Hydrocarbons. 

The  hydrocarbons  are  organic  compounds  of  carbon  and 
hydrogen  only.  The  simplest  of  these  is  marsh-gas  or  methane 
(CH4).  The  molecule  of  this  substance  consists  of  a  single 
carbon  atom  with  each  of  its  four  points  of  atomic  attraction 
(valence)  satisfied  by  an  atom  of  hydrogen. 

H^     /H 
C 

If  one  of  these  four  atoms  of  H  is  replaced  by  a  chlorin  atom, 
for  instance,  we  have  a  substitution  product.  Its  formula  will 
be  CH3CI,  its  name  monochlormethane  or  methyl  chlorid.  If 
two  molecules  of  methyl  chlorid  are  brought  together  and 
the  CI  removed  by  metallic  sodium  the  residual  molecules 
(methyl  radicals)  will  unite,  forming  a  new  hydrocarbon,  as 
follows : 

2  CH3CI  +  Na2  =  2  NaCl  +  CaHg  (ethane). 


THE  HYDROCARBONS  AND  SUBSTITUTION  PRODUCTS      1 85 

By  a  similar  reaction  we  may  form  the  third  member  of 
the  series,  CsHs  (propane),  from  ethyl  chlorid  (C2H5CI)  and 
sodium;  the  fourth  member,  butane,  C4H10,  from  propyl  chlorid, 
etc.  A  tabulated  list  of  the  first  five  compounds  of  this  series 
will  plainly  show  their  chemical  relationship : 

CH4,  methane  or  methyl  hydrid  (CH3H). 
C2H6,  ethane  or  ethyl  hydrid  (C2H5H). 
CsHg,  propane  or  propyl  hydrid  (C3H7H). 
C4H10,  butane  or  butyl  hydrid  (C4H9H). 
C5H12,  pentane  or  amyl  hydrid  (C5H11H). 

Note  that  the  various  members  of  this  series  differ  from  one 
another  by  CH2;  that  is,  each  higher  compound  contains  one 
carbon  atom  and  two  hydrogen  atoms  more  than  its  predecessor. 
This  holds  true  through  the  series,  and  the  compounds  of  this 
or  any  such  series  are  termed  homologues  and  the  series  ho- 
mologous series.  Note  further  that  any  member  of  this  series 
(which  is  known  as  the  paraffin  series)  may  be  represented  by 
the  general  formula  CnH2n+2-  This  likewise  holds  true  through- 
out the  series,  and  a  compound  having  sixty  carbon  atoms  will 
have  a  formula  of  C60H122.  The  first  four  hydrocarbons  of 
this  series  are  gaseous  at  ordinary  temperatures;  from  C5H12  to 
about  C16H34  the  hydrocarbons  are  liquid;  from  C16H34  (melt- 
ing at  about  18°)  up  they  are  solids. 

Isomers.  —  When  two  or  more  compounds  are  of  exactly 
the  same  molecular  composition  in  regard  to  numbers  and  kind 
of  atoms,  they  are  isomeric  substances  or  isomers. 

Thus  we  may  have  a  normal  butane  represented  graphically 

HHHH 

1     I     I     I 
by  H-C-C-C-C-H  (C4H10),  then  we  may  have  an  isomeric  or 

HHHH 

isobutane  represented  by 


l86  ORGANIC  CHEMISTRY 


H 

H        H 

\     / 

H 

C 

1 

-c{          H 

H-C- 

1 

l\    / 

H 

H     ^C-H 

\ 

H 

also  C4H10,  but  having  different  physical  and  chemical  properties 
from  the  normal  compound.  The  greater  the  number  of  carbon 
atoms  in  the  molecule,  the  more  numerous  the  possible  isomers. 

Polymers.  —  When  one  compound  has  a  formula  which  may 
be  regarded  as  a  multiple  of  another,  it  is  said  to  be  a  polymer 
of  it;  thus,  paraform,  a  white  crystalline  solid,  (CH20)3,  is  a 
polymeric  form  of  the  gaseous  formaldehyd,  CH2O. 

The  hydrocarbons  of  the  paraffin  series  are  known  as  straight 
chain  or  aliphatic  hydrocarbons,  their  graphic  formulae  consist- 

ing  of  '  chains"  of  carbon  atoms,  as  butane,  -C-C-C-C-,  in 

I     I     I     I 
distinction  from  the  closed-chain  or  cyclic  compounds  as  repre- 
sented by  the  "benzole-ring"  (page  240)  carbon  nucleus  with 
the  C  atoms  united  in  a  continuous  closed  chain  or  "  cycle." 

The  paraffins  are  called  saturated  hydrocarbons  because 
they  are  incapable  of  forming  addition  products  by  absorption 
of  CI,  for  instance,  without  first  giving  off  an  equivalent  num- 
ber of  atoms  of  H.  This  is  because  of  the  complete  "  satu- 
ration" or  union  of  every  carbon  "bond"  with  some  other 
atom.*  Paraffin  wax  and  mineral  oil  are  mixtures  of  saturated 
hydrocarbons  and  resist  chemical  action  even  of  strong  nitric 
acid  or  sulphuric  acid. 

The  natural  sources  of  hydrocarbons  of  the  paraffin  series 

*  Notice  that  while  addition  products  of  saturated  hydrocarbon  cannot  be 
formed,  substitution  products  are  easily  possible.     See  page  184. 


THE  HYDROCARBONS  AND  SUBSTITUTION  PRODUCTS      187 


are  natural  gas  and  crude  petroleum, 
or  rock  oil.  Many  of  these  hydro- 
carbons exist  as  such  in  the  petro- 
leum, and  some  undoubtedly  are 
produced  by  the  heat  used  to  effect 
a  separation  of  the  various  com- 
pounds. This  separation  is  effected 
by  distilling  the  oil  in  an  apparatus 
similar  to  that  pictured  in  Fig.  15, 
and  is  known  as  fractional  distillation, 
the  different  hydrocarbons  passing 
over  at  different  temperatures.  Sep- 
aration by  this  method,  however,  is 
by  no  means  complete,  and  the 
resulting  products  are  themselves 
mixtures  of  hydrocarbons,  and  are 
distinguished  by  physical  depravities 
rather  than  by  chemical  composition. 
When  crude  petroleum  is  thus 
distilled,  the  following  products  are 
obtained :  first,  rhigoline,  which  comes 
over  at  a  temperature  of  20°  to  22° 
C;  then  petroleum  ether  or  benzine 
at  from  50°  to  60°  C;  then  gasolene 
or  naphtha  at  about  75°  C;  then  i 
or  2  unimportant  commercial  pro- 
ducts, and  kerosene  or  burning  oil  is 
obtained  at  150°  to  250°  C.  Above 
this,  we  may  obtain  parafffn  oil  or 
light  lubricating  oils;  then  the  heavy 
lubricating  or  cylinder  oils,  and  from 
the  residue  we  obtain  the  solid  sub- 
stances known  as  vaseline  or  petrola- 
tum and  paraffin  of  various  degrees 
of  hardness. 


Fig.  15. 


l88  ORGANIC  CHEMISTRY 

The  first  five  hydrocarbons  of  this  series  we  will  consider 
somewhat  in  detail,  not  only  because  they  are  important  and 
comparatively  common,  but  also  because  they  serve  as  types  of 
all  other  compounds  of  the  series  and  reactions  which  we  study 
with  these  compounds,  or,  as  a  rule,  general  typical  reactions 
which  may  be  produced  with  other  members  of  the  series. 

Methane,  CH4,  occurs  as  marsh  gas  in  stagnant  ponds  or 
pools  and  is  a  constituent  of  "  fire  damp"  in  coal  mines.  It  is 
a  colorless  gas,  odorless  when  pure,  and  very  slightly  soluble 
in  water.  It  may  be  prepared  artificially  by  the  decomposition 
of  anhydrous  sodium  acetate,  with  sodium  hydroxid  and  lime. 
See  reaction  on  page  191,  Exp.  50.  Methane  burns  in  the  air 
with  the  production  of  carbon  dioxid  and  water 

CH4  +  2  O2  =  CO2  +  2  H2O. 

Ethane,  C2H6,  the  second  member  of  the  series,  occurs  natur- 
ally in  a  solution  in  crude  petroleum,  and  can  be  artificially  pre- 
pared by  the  electrolytic  decomposition  of  a  saturated  solution 
of  potassium  acetate  as  follows: 

2  CH3COOK  =  C2H6  +  2  CO2  -f  K2. 

The  free  potassium,  of  course,  decomposes  H2O,  Hberat- 
ing  hydrogen  gas  which  collects  at  the  negative  pole,  and,  if 
the  solution  contains  sufficient  KOH,  the  CO2  will  be  dissolved, 
allowing  C2H6  to  collect  at  the  positive  pole. 

Ethane  may  also  be  made  from  a  haloid  derivative  of  marsh 
gas  by  the  action  of  metalHc  sodium;  that  is,  in  CH4  we  may 
replace  one  of  the  hydrogen  atoms  with  iodin,  forming  CH3I 
of  methyl  iodid;  then  by  treatment  with  metalHc  sodium,  the 
following  reaction  will  take  place: 

2  CH3I  +  2  Na  =  C2H6  +  2  Nal. 

Ethane  is  slightly  more  soluble  in  water  than  methane.  It 
may  be  condensed  to  a  liquid  at  a  pressure  of  46  atmospheres. 


THE  HYDROCARBONS  AND  SUBSTITUTION  PRODUCTS      189 

Propane,  CsHg,  also  occurs  in  petroleum,  and  can  be  made  by- 
treating  a  mixture  of  ethyl  iodid  and  methyl  iodid  with  metalHc 
sodium : 

C2H5I  +  CH3I  +  2  Na  =  C3H8  +  2  Nal. 

This  is  a  general  method  for  building  up  hydrocarbon  com- 
pounds. Propane  at  ordinary  atmospheric  pressure  is  con- 
densed to  Hquid  at  17°  below  zero. 

Butane,  C4H10,  is  the  first  of  the  series  capable  of  existing  in 
two  forms,  isomers.  The  structural  formulae  of  these  two  com- 
pounds are  shown  in  the  illustration  of  the  term  isomer  on 
page  185.  This  compound,  as  well  as  the  next  higher  homologue 
pentane,  C5H12,  are  of  importance  only  in  their  relation  to  some 
of  their  derivatives  which  will  be  subsequently  studied. 


DOUBLE-BONDED   HYDROCARBONS. 

If  two  carbon  atoms  are  united  by  a  double  bond,  as  in 
H  H 

^C  =  C^(C2H4),    chlorin    may    be    added    directly    by    the 
H  H 

breaking    of     the    double    bond,    forming    ethylene    chlorid, 

C2tL4d2. 

Note  that  the  formula  of  ethylene  does  not  conform  to  the 
general  formula  of  the  paraffins  (CnH2n+2),  but  is  the  first 
member  of  the  new  series  of  "unsaturated"  hydrocarbons; 
the  olefin  or  ethylene  series  with  a  general  formula. of  CnH2n. 

The  hydrocarbons  of  this  series  take  their  names  from  corre- 
sponding members  of  the  parafiin  series,  with  "ene"  as  a  dis- 
tinguishing termination  —  ethylene,  C2H4,  propylene,  C2H6, 
butylene,  C5H10,  etc.  They  are  unimportant  in  dental  or  physio- 
logical chemistry.  Some  of  the  higher  oxygenated  compounds 
of  this  class  are,  however,  of  great  importance,  as  olein,  which 
is  a  constituent  of  vegetable  and  animal  fats  and  oils. 


I  go  ORGANIC  CHEMISTRY 

TRIPLE-BONDED   HYDROCARBONS. 

A  third  series  of  the  straight  chain  hydrocarbons  is  the 
acetylene  series;  these  are  triple  bonded,  and  of  course  unsatu- 
rated, with  a  general  formula  of  CnH2n-2- 

The  only  members  of  this  series  of  special  interest  are,  first, 
acetylene,  H  —  C  =  C  —  H,  (C2H2),  made  from  calcium  carbid 
and  water.  It  is  poisonous,  combining  directly  with  the  haemo- 
globin of  the  blood,  has  a  disagreeable  odor,  and  is  inflammable; 
second,  allylene,  C3H4,  derivatives  of  which  occur  in  onions^ 
garlic,  mustard-oil,  etc. 

Laboratory  Exercise  LI. 
Experiments  with  Carbon  and  Hydrocarbons. 

Exp.  45.  Carbon  as  a  decolorizing  agent.  To  25  or  30  c.c. 
of  a  dilute  solution  of  aniline  color,  contained  in  a  small  beaker, 
add  a  teaspoonful  of  bone  charcoal.  Heat  to  the  boiling-point, 
rotate  or  stir  thoroughly  for  a  few  minutes,  and  filter. 

Exp.  46.  Absorption  of  metallic  salts.  To  25  c.c.  of  solu- 
tion of  lead  acetate  of  such  strength  that  H2S  water  gives  marked 
color  but  no  precipitate,  add  a  teaspoonful  of  bone  charcoal  and 
treat  as  in  preceding  experiment.  Test  the  filtrate  with  II2S 
water  and  note  whether  lead  has  been  removed. 

Exp.  47.  Perform  an  experiment  with  a  view  to  determin- 
ing whether  bone  charcoal  will  absorb  H2S  from  H2S  water. 

Exp.  48.  Repeat  either  of  the  three  immediately  preceding 
experiments,  using  wood  charcoal  in  place  of  bone  charcoal. 
Does  the  wood  charcoal  work  as  well  as  the  bone  charcoal  in 
the  absorption  of  color  or  other  substances?  How  does  bone 
charcoal  differ  in  composition  from  wood  charcoal  ? 

Exp.  49.  25  c.c.  of  crude  petroleum  in  a  boiling  flask  is 
connected  with  a  long  piece  of  tubing  which  serves  as  an  air 
condenser.  The  flask  is  fitted  to  the  thermometer  and  the 
contents  heated  slowly  until  at  least  three  fractional  products 


THE  HYDROCARBONS  AND  SUBSTITUTION  PRODUCTS      19I 

are  obtained  with  boiling  points  differing  by  at  least  15°.  Note 
any  other  physical  differences  between  the  distillates  thus  ob- 
tained. 

Exp.  50.  Charge  an  ignition- tube  with  dry  "marsh-gas 
mixture,"  found  on  side  shelf  (consisting  of  NaC2H302,  NaOH, 
and  Ca02H2).  Fit  with  a  delivery- tube  and  collect  two  small 
bottles  of  the  gas  over  water. 

NaC2H302  -I-  NaOH  =  CH4  -|-  Na2C03. 

Test  the  inflammability  of  this  gas.     Notice  the  odor. 

Exp.  51.  Mix  carefully  in  a  test-tube  2  c.c.  of  alcohol  and 
8  c.c  of  strong  sulphuric  acid.  Heat  gently  and  notice  odor  of 
gas.  Fit  a  bent  glass  tube  to  the  test-tube  and  collect  over 
water  a  test-tube  full  of  the  gas.  To  this  apply  a  flame.  Note 
the  color  of  the  burning  gas. 

C2H5OH  —  H2O  =  C2H4. 

Haloid  Derivatives  of  the  Paraffins. 

Methane  furnishes  three  chlorin  substitution  products  which 
are  more  or  less  in  common  use :  first,  the  monochlor-methane,  or 
methyl  chlorid ;  second,  the  trichlor-methane  CHCl  or  chloroform, 
and  third,  the  tetrachlorid  of  carbon  CCI4. 

Methyl  Chlorid,  CH3CI,  may  be  made  from  methyl  alcohol, 
zinc  chlorid,  and  hydrochloric  acid.  It  is  a  colorless  gas,  con- 
densing to  a  liquid  at  23°  C;  used  as  a  spray  in  producing  local 
anaesthesia  (page  172);  also  as  a  constituent  of  anaesthetics,  such 
as  anesthol,  somnoform,  etc. 

Dichlor-methane,  CH2CI2,  also  known  as  methylene  chlorid, 
has  been  used  as  a  general  anaesthetic  usually  mixed  in  more  or 
less  chloroform  and  alcohol.  Its  use  in  this  way  is  open  to 
criticism  because  of  its  poisonous  action,  affecting  the  heart. 

Chloroform,  CHCI3,  trichlormethane,  is  a  general  anaesthetic 
prepared  by  distilling  a  mixture  of  chlorinated  lime  and  acetone. 
Alcohol  and  water  were  formerly  used  in  place  of  acetone  (see 


192  ORGANIC  CHEMISTRY 

Exp,  56,  page  193).  While  it  is  not  regarded  as  inflammable, 
its  heated  vapor  can  be  made  to  burn  with  a  greenish  flame. 

Methyl  Chloroform,  CH3CCI3,  formed  by  replacing  the  H 
atom  of  chloroform  by  a  methyl  group,  CH3,  has  been  used  as 
an  ansesthetic. 

Tetrachlorid  of  carbon  is  a  colorless  liquid  used  quite  largely 
as  a  solvent.  It  also  has  ansesthetic  properties,  but  like  dichlor- 
methane,  is  dangerous  because  of  its  action  on  the  heart. 

Methyl  bromid,  or  monobrom-methane,  is  used  to  some  ex- 
tent as  a  constituent  of  anaesthetics . 

Bromoform,  CHBrs,  tribrom-methane,  is  prepared  from 
bromin  and  a  solution  of  alcoholic  potash.  Its  properties  are 
similar  to  those  of  chloroform,  but  it  is  more  poisonous. 

Methyl  lodid,  CH3I,  is  a  heavy  liquid,  with  pleasant 
odor,  boiling-point  43°  C;  has  been  used  somewhat  as  a 
vesicant. 

Iodoform,  HCI3,  tri-iodomethane,  is  a  much-used  and  very 
valuable  antiseptic.  It  is  a  light-yellow  crystalline  powder 
with  characteristic  persistent  odor  (Plate  V,  Fig.  i,  page  222). 

Iodoform  may  be  made  by  heating  in  a  retort  two  parts  of 
potassium  carbonate,  two  of  iodin,  one  of  strong  alcohol,  and  five 
of  water,  till  the  mixture  is  colorless. 

Iodoform  is  also  produced  from  action  of  the  above  reagents 
with  acetone  in  place  of  alcohol.  This  test  is  a  very  deli- 
cate one  and  advantage  is  taken  of  it  in  testing  for  acetone  in 
saliva,  which  see. 

Ethyl  Chlorid,  C2H5CI,  chlorethyl,  may  be  made  by  dis- 
tillation of  a  mixture  of  alcohol  and  hydrochloric  acid  and 
purification  of  the  distillate.  It  is  extremely  inflammable,  boils 
at  12°  C,  and  is  used  as  a  local  anaesthetic  in  similar  manner  to 
methyl  chlorid.  Its  higher  boiling-point  makes  it  the  more 
convenient  of  the  two  preparations  (see  page  169). 

Ethyl  Bromid,  C2H5Br,  prepared  from  alcohol,  sulphuric 
acid,  and  potassium  bromid.     It  is   a  heavy   colorless  liquid, 


THE  HYDROCARBONS  AND  SUBSTITUTION  PRODUCTS      193 

does  not  burn,  and  has  been  used  to  considerable  extent  as  a 
general  aneesthetic. 

Laboratory  Exercise   LII. 

Experiments  with   Hydrocarbons  (continued)  and   their  Halogen 

Derivatives. 

Exp.  No.  52.  Shake  together,  in  separate  test-tubes,  small 
quantities  of  petroleum  and  sulphuric  acid  in  one  tube,  and 
petroleum  and  nitric  acid  in  the  other.  If  no  action  results,  mix 
contents  of  the  two  tubes  and  shake  again.  Explain  any  change 
or  absence  of  change  which  may  be  apparent. 

Exp.  53.  In  a  small  generator  (see  model)  place  a  few  small 
pieces  of  calcium  carbid  (CaC2),  add  strong  alcohol  through  the 
funnel  tube  till  the  lower  end  of  the  tube  is  "sealed."  Now 
add  very  slowly  a  little  water  till  a  brisk  evolution  of  gas  is 
obtained.  Collect  over  water  two  or  three  test-tubes  full  of  the 
gas.     (Acetylene.) 

Test  with  a  lighted  splinter.  Note  odor  of  gas  cautiously, 
as  it  is  poisonous  when  inhaled  in  quantity. 

CaCa  -f  2  H2O  =  Ca(0H)2  +  C2H2. 

Exp.  54.  Conduct  a  little  of  the  acetylene  gas  into  an  am- 
moniacal  cuprous  chlorid  solution.     What  is  the  red  precipitate  ? 

Exp.  55.  If  the  evolution  of  gas  has  not  been  interrupted 
the  delivery-tube  may  be  replaced  by  a  short  tube  drawn  out 
to  a  fine  point  and  the  gas  ignited.  Note  color  of  flame.  If 
it  smokes  badly,  explain  the  reason  for  it. 

Exp.  56.  Place  in  a  test-tube  a  Httle  bleaching-powder, 
cover  with  strong  alcohol  and  heat  the  mixture  to  boiling. 
Notice  carefully  the  odor  of  the  vapor  produced  and  compare 
with  a  little  chloroform  (CHCI3)  from  side  shelf. 

4  C2H5OH  -F  8  Ca(C10)2  =  2  CHCI3  +  3  Ca(CH02)2 

(Formate  of  Ca) 

+  5  CaCl2  +  8  H2O. 


194  ORGANIC  CHEMISTRY 

Exp.  57.  Place  in  a  test-tube  about  i  gram  of  crystallized 
carbonate  of  sodium,  about  half  as  much  iodin  and  i  or  2  c.c.  of 
alcohol.  Now  add  10  or  15  c.c.  of  H2O  and  keep  the  mixture 
at  moderate  heat  (not  boihng)  till  the  color  of  the  iodin  is  dis- 
charged. Allow  to  cool;  collect  on  a  small  filter-paper  some  of 
the  yellow  crystals  which  have  been  formed  and  examine  under 
the  microscope.  What  are  the  crystals?  Explain  their  rela- 
tion to  marsh-gas. 


CHAPTER  XXII. 
ALCOHOLS. 

If  we  substitute  for  one  of  the  hydrogen  atoms  of  methane, 
a  hydroxyl  group  (OH),  we  shall  produce  the  first  of  a  series  of 
alcohols,  several  of  which  will  claim  our  attention. 

The  alcohols  may  be  considered  as  hydroxids  of  alkyl  *  radi- 
cals, CH3OH  being  methyl  alcohol;  C2H5OH,  being  ethyl  or 
ordinary  alcohol;  C3H7OH  being  propyl  alcohol;  and  C5H11OH, 
amyl  alcohol  or  fusel  oil. 

The  alcohols  as  a  class  may  be  prepared  by  the  action  of 
moist  silver  oxid  on  the  corresponding  halogen  compounds;  e.g., 

CHgBr  +  AgOH  =  CH3OH  +  AgBr. 

In  many  instances,  the  alkaline  hydroxids  will  act  in    the 

same  way. 

CHsBr  +  KOH  =  CH3OH  +  KBr. 

Alcohols  treated  with  metallic  sodium  or  potassium  liberate 
hydrogen  gas,  forming  compounds  known  as  alcoholates;  e.g., 

CH3OH  +  K  =  CH3OK  +  H; 
or  C2H5OH  +  K  =  C2H5OK  +  H. 

While  these  compounds  are,  as  just  stated,  called  alcoholates, 
they  may  be  distinguished,  one  from  another,  by  using  the  name 
of  the  alkyl  radical  involved,  and  CH3OK  will  be  potassium 
methylate,  while  C2H5OK  will  be  potassium  ethylate. 

Alcohols  may  contain  more  than  one  hydroxyl  group,  and, 

*  Alkyl— a  term  used  to  denote  any  hydrocarbon  radical  as  CH3-,  C2H5-,  C3H7-, 
etc. 

19s 


196  ORGANIC  CHEMISTRY 

according  to  number  of  the  OH  groups,  are  termed  mono-,  di-, 
tri-atomic,  etc.  Thus,  ordinary  alcohol,  C2H5OH,  is  mono- 
atomic;  glycerol,  C3H5(OH)3  is  triatomic,  while  mannite 
C6H8(OH)6  is  a  hexatomic  alcohol. 

Alcohols  may  also  be  classified  according  to  the  relative 
position  of  the  hydroxyl  group.  By  this  classification,  we  may 
have  primary  alcohols  with  OH  replacing  a  hydrogen  of  the 
-CH3  group;  secondary  alcohols  with  OH  replacing  the 
hydrogen  of  a  -CH2  group;  and  tertiary  alcohol  with  OH  re- 
placing the  hydrogen  of  a  -CH  group.  This  may  be  illus- 
trated by  the  formula  of  an  alcohol  of  each  class.  CH3-CH2 
-CH3,  being  the  hydrocarbon,  a  primary  alcohol  will  have  the 
formula  CH3.CH2.CH2OH,  and  -CH2OH  may  be  considered 
distinctive  grouping  of  the  primary  alcohols.  Again  from  the 
same  hydrocarbon,  if  OH  is  substituted  for  an  H  of  CH2 
then  the  secondary  alcohol  will  be  CH3-CHOH-CH3  and 
-CHOH  may  be  regarded  as  a  distinctive  group  of  this  class. 

The  tertiary  alcohols,  however,  must  be  produced  from  com- 
pounds having  at  least  four  carbon  atoms,  as  a  CH  group  is 
only  possible  when  there  are  sufficient  carbon  atoms  to  produce 
a  forked  chain ;  that  is,  in  a  compound  with  three  carbon  atoms, 
one  must  of  necessity  be  placed  between  the  other  two,  while 
with  four  carbon  atoms,  the  carbons  may  be  attached  in  a 
straight  chain,  such  as  C--C-C-C,  or  they  may  be  arranged  as 

/C 
a  forked  chain  C-C  ,^     ,  and  by  supplying  the  hydrogen  atoms 

necessary  to  satisfy  the  valence  of  each  carbon,  in  this  latter 
chain  we  find  a  CH  group.  OH  introduced  in  place  of  the 
hydrogen  of  this  group  gives  us  the  tertiary  alcohol, 

/  CH3 
CH3-C0H(^^. 

Notice  that  the  forked  chain  gives  us  possible  isomeric  com- 
pounds. 


ALCOHOLS  197 

The  hydroxyl  derivatives  (alcohols)  of  isopentane  are  well 
suited  to  illustrate  the  three  (primary,  secondary,  and  tertiary) 
characteristic  alcohol  groupings. 

CH3\ 
CHa 


.  CH-CH2-CH3  is  isopentane 


and  by  introducing  the  OH  group   (hydroxyl)   into  the  CH3 
group  there  is  formed  a  primary  amyl  alcohol, 

CH. 


L3\ 

CH 


CH-CH2CH2OH,  or  isobutyl  carbinol. 


and  the  primary  alcohol  grouping  is  -CH2OH.  By  introducing 
hydroxyl  (OH)  into  the  CH2  group  we  should  have  -CHOH- 
as  a  characteristic  combination  in  secondary  alcohols, 

CHs  \ 
CH, 


^  CH-CHOH-CH3,  methylisopropyl  carbinol; 


and  lastly,  by  putting  the  OH  in  place  of  the  H  of  the  CH  group 
of  the  hydrocarbon,  we  should  have  (CH3)2  =  COH-CH2-CH3, 
a  tertiary  alcohol  with  the  group  =  COH  as  its  characteristic. 

Methyl  Alcohol,  CH3OH,  (H-CH2OH),*  wood  spirit,  carbi- 
nol, is  a  product  of  the  destructive  distillation  of  wood  or  can 
be  made  synthetically  from  methane.  It  is  a  colorless,  inflam- 
mable hquid,  with  a  gravity  of  0.802  at  15°  C,  with  solvent 
properties  similar  to  ordinary  alcohol,  and  boils  at  66°. 

Ethyl  Alcohol,  C2H5OH,  (CH3-CH2OH),  methyl  carbinol, 
grain  alcohol,  or  ordinary  alcohol  is  made  by  fermentation  of 
solutions  of  various  carbohydrates  and  purified  by  distillation. 
Carbon  dioxid  is  evolved  as  follows : 

CeHiaOe  =  2  C2H5OH  +  2  CO2. 

95%  alcohol  has  a  specific  gravity  0.8164,  boils  at  about 
78°  C,  dissolves  many  inorganic  salts,  vegetables,  waxes,  resins 

*  Note  that  CH2OH  is  the  "alcohol  group"  pecuhar  to  this  class  of  alcohols- 


igS  ORGANIC  CHEMISTRY 

(not  gums),  oils,  etc.,  and  is  miscible  with  water,  ether,  or 
chloroform. 

Amyl  Alcohol,  C5H11OH,  (C4H9-CH2OH),  isobutyl  carbinol, 
is  a  colorless,  oily  liquid  with  a  specific  gravity  of  0.818.  It 
boils  at  about  130°  C,  and  burns  with  a  bluish  flame. 

Fusel-oil,  or  potato  spirit,  consists  of  amyl  alcohol  carrying 
traces  of  various  other  alcohols  as  impurities. 

Amyl  alcohol  is  a  valuable  solvent  and  is  largely  used  in  the 

manufacture  of  artificial  fruit  flavors,  banana  essence,  and  the 

like. 

Oxidation  of  the  Alcohols. 

Aldehyds. 

The  first  step  in  the  oxidation  of  an  alcohol  consists  not  in 

the  addition  of  oxygen  but  in  the  withdrawal  of  hydrogen;  thus 

the  oxidation  of  methyl  alcohol  produces  formaldehyd  (CH2O) 

and  water. 

CH3OH  +  0  =  CH2O  +  H2O. 

Aldehyds  may  be  considered  compounds  containing  an  alkyl 

H  H 

/  I 

radical  and  a  distinctive  group,  -C   ;  thus  CHO  is  formaldehyd, 

O 
CH3,  is  acetaldehyd,  etc.  (compare  Alcohol,  page  197). 
I 
CHO 

Formaldehyd  coagulates  albumen  and  hardens  gelatin;  when 
used  as  a  preservative  it  renders  the  proteins  tougher  and  less 
digestible. 

Formaldehyd  polymerizes,  producing  the  paraform  or  para- 
formaldehyd  of  trade,  trioxymethylene,  with  a  probable  for- 
mula of  (CH20)3.  It  also  forms  one  lower  polymer  (CH20)2  and 
at  least  one  higher,  formose,  a  substance  aUied  to  glucose. 

Acetaldehyd,  aldehyd,  CH3-CHO  or  C2H4O,  the  aldehyd 
from  ethyl  alcohol,  may  be  made  by  addition  of  H2SO4  to  a 


ALCOHOLS  199 

mixture  of  alcohol  and  bichromate  of  potassium.  It  is  a  color- 
less, inflammable  Hquid  with  pungent  etherial  odor  and  boils 
at  22°  C. 

Paraldehyd,  (C2H40)3  a  polymer  of  acetaldehyd,  is  a  "  color- 
less liquid  with  a  strong  pungent  odor,  soluble  in  8.5  parts  of 
water  at  15°  C,  miscible  in  all  proportions  with  alcohol,  ether, 
and  fixed  or  volatile  oils. "     (U.  S.  P.)     It  is  a  valuable  hypnotic. 

Chloral,  CCI3CHO,  trichloraldehyd,  is  an  oily  liquid  formed 
by  action  of  dry  CI  gas  on  pure  alcohol;  soluble  in  ether  and 
chloroform,  boiling  at  from  94°  C.  to  98°  C,  and  forming,  with 
a  molecule  of  H2O  chloral  hydrate,  CCI3CHO.H2O,  a  crystalline 
solid,  and  this  is  the  "chloral"  of  the  pharmacopoeia  (see  page 
167). 

Chloral   hydrate  is  decomposed   by  sodium  or  potassium 
hydrate  with  Hberation  of  chloroform  (see  Exp.  72,  page  211): 
CCI3-CHO  +  KOH  =  CHCI3+  KCOOH  (potassium  formate). 

Upon  warming  a  drop  or  two  of  aniline  oil  in  an  excess  of 
alcoholic  potash,  chloral  hydrate  forms,  first,  chloroform,  then 
phenylisocyanid,  CeHsNC,  the  persistent  disagreeable  odor  of 
which  furnishes  a  dehcate  test  for  chloroform  or  chloral  (see 
Exp.  73,  page  211).  By  using  CHCI3  as  the  reagent  in  place  of 
the  aniline,  the  same  reaction  becomes  a  test  for  aniline  or 
organic  compounds,  from  which  aniline  may  be  produced  by 
heating  with  alcoholic  potash  as  acetanihd.  Other  aldehyds 
from  hexatomic  alcohols  are  dextrose  (glucose)  and  galactose. 
They  are  represented  by  the  formula  CH20H-(CHOII)4-CHO, 
and  will  be  considered  more  fully  in  a  subsequent  lecture. 

Laboeatory  Exercise  LIII. 

Alcohols  and  Aldehyds. 

Exp.  58.  The  detection  of  water  in  alcohol.  Prepare  a 
httle  anhydrous  copper  sulphate  by  heating  a  few  crystals  of 
CUSO4  on  a  crucible  cover  until  the  water  is  driven  off  and  a 


200  ORGANIC  CHEMISTRY 

nearly  white  powder  results.  If  this  white  powder,  after  boil- 
ing, is  added  to  a  half  a  test-tube  full  of  alcohol,  the  absorption 
of  water,  if  present,  will  result  in  reforming  the  crystalHzed  salt 
-and  a  consequent  production  of  blue  color. 

Exp.  59.  Water  may  be  separated  from  alcohol  by  saturat- 
ing with  potassium  carbonate.  To  demonstrate  this,  take  a 
mixture  of  alcohol  and  water,  containing  15  or  20  per  cent  of 
alcohol,  and  add  soHd  potassium  carbonate  until  the  salt  will 
no  longer  dissolve.  Agitate  and  allow  to  stand.  Two  layers 
will  form,  one  consisting  of  alcohol  the  other  of  the  water  solu- 
tion of  K2CO3. 

Exp.  60.  To  about  75  c.c.  of  a  10%  glucose  solution  add 
a  little  yeast  and  allow  to  stand  for  twenty-four  hours  at  a 
temperature  of  about  37°  C;  then  distil  by  means  of  gentle 
heat  10  or  15  c.c,  and  test  distillate  for  alcohol  by  iodoform  test, 
as  given  on  page  194,  Exp.  57.  The  production  of  CO2  may 
also  be  demonstrated  if  the  gases  evolved  during  the  fermentation 
are  passed  into  clear  lime-water: 

CeHiaOe  =  2  C2H5OH  +  2  CO2. 

Exp.  61.  A  test  for  methyl  alcohol.  This  test  is  applicable 
only  to  slight  traces  of  methyl  alcohol  and  may  be  made  with 
a  I  to  2  per  cent  solution  or  with  the  first  cubic  centimeter  of 
distillate  from  the  substance  suspected  of  containing  methyl 
alcohol.  Place  2  or  3  c.c.  of  very  dilute  methyl  alcohol  in  a 
test-tube,  heat  a  spiral  of  copper  wire  to  white  heat  in  a  Bunsen 
flame  and  plunge  immediately  into  the  solution  to  be  tested. 
Cool  the  contents  of  the  tube  by  immersion  in  freezing  mixture 
or  ice  water,  and  repeat  the  treatment  with  the  hot  copper  wire. 
Cool  again,  and  a  third  time  introduce  the  hot  copper  wire. 
The  copper  spiral  can  be  made  by  winding  copper  wire  around  a 
lead  pencil,  and  should  be  of  such  a  length  that  it  is  not  wholly 
covered  by  the  Hquid  in  the  tube. 

This  process  serves  to  oxidize  a  portion  of  the  alcohol  to 


ALCOHOLS  201 

aldehyd.  Now  add  to  the  solution  which  is  being  tested  a  few 
drops  of  a  1/2%  water  solution  of  resorcin  and  underlay  the 
mixture  with  strong  sulphuric  acid.  A  violet  ring  will  indicate 
the  presence  of  methyl  alcohol.  The  higher  alcohols  will  give 
red  or  brown  rings  when  similarly  treated. 

Exp.  62.  Mix  about  i  c.c.  of  a  very  dilute  solution  of 
formaldehyd  with  four  or  five  times  its  volume  of  milk  in  a  test- 
tube.  Carefully  underlay  the  mixture  with  commercial  sul- 
phuric acid  of  a  specific  gravity  of  1.80.  At  the  point  of  contact 
of  the  two  layers  of  Hquid  a  violet-colored  ring  indicates  the 
presence  of  formaldehyd.  It  is  necessary  that  the  sulphuric 
acid  should  contain  a  trace  of  iron :  this  the  commercial  acid  usu- 
ally does.  It  is  also  undesirable  that  the  acid  should  be  stronger 
than  of  1.80  specific  gravity;  for,  if  it  is,  a  reddish-brown  ring 
may  be  formed,  due  to  partial  carbonization  of  the  casein. 

Exp.  63.  To  about  5  c.c.  of  a  strong  aqueous  solution  of 
potassium  dichromate  add  a  little  sulphuric  acid,  then  a  few 
cubic  centimeters  of  alcohol,  and  notice  the  odor  of  acetaldehyd 
produced  by  oxidation  of  the  alcohol.  Note  also  the  reduction 
of  the  dichromate  to  Cr2(S04)3,  as  follows: 

KsCrsOy  +  4  H2SO4  +  3  C2H5OH  = 

K2SO4  +  Cr2(S04)3  +  3  C2H4O  -f  7  H2O. 

Exp.  64.  Test  a  dilute  solution  of  both  formic  and  acetic 
aldehyd  by  Tollen's  test  for  aldehyd  as  follows:  Into  a  clean 
test-tube  which  has  been  rinsed  with  NaOH  solution,  place  5  c.c. 
of  Tollen's  reagent,  add  10  c.c.  of  solution  to  be  tested,  shake; 
the  silver  is  reduced,  forming  a  metallic  mirror  on  the  inner  sur- 
face of  the  tube. 

To  make  Tollen's  reagent,  dissolve  3  grams  of  silver  nitrate 
in  30  c.c.  ammonia  water  and  add  3  c.c.  of  solution  of  sodium 
hydroxid. 


202  ORGANIC  CHEMISTRY 


Ketones. 

The  oxidation  of  secondary  alcohols  (page  196)  will  not  yield 
aldehyds,  but  a  class  of  substances  known  as  ketones: 

(CH3)2-CH-CHOH-CH3  +  O  =(CH3)2-CH-C  :  O-CH3+  H2O, 

A  secondary  alcohol.  Methyl  isopropyl  ketone. 

Methyl  isopropyl  carbinol. 

or  CH3-CHOH-CH3  +  0  =  CH3-CO-CH3  +  H2O. 

Isopropyl  alcohol.  Dimethyl  ketone. 

The  converse  of  each  of  these  reactions  is  possible,  and,  by 
reduction  of  a  ketone  with  nascent  H  (sodium  amalgam),  the 
secondary  alcohol  will  be  formed: 

CH3-CO-CH3  +  H  =  CH3-CHOH-CH3. 

Acetone.  Isopropyl  alcohol. 

Likewise  primary  alcohols  may  be  produced  by  the  reduc- 
tion of  aldehyds: 

CH3-CHO  +  H2  =  CH3-CH2OH. 

Acetaldehyd.  Ethyl  alcohol. 

Note  that  the  grouping  peculiar  to  ketone  is  =  CO  or  -CO-. 

Acetone,  or  dimethylketone,  CH3-CO-CH3,  a  colorless  liquid 
of  peculiar  odor,  boils  at  56°  C.  and  is  made  commercially  by 
the  dry  distillation  of  acetate  of  lime. 

It  occurs  in  the  blood  and  urine  of  patients  suffering  from 
advanced  diabetes.  According  to  von  Noorden,  the  acetone 
found  in  the  blood  is  formed  by  an  intracellular  process  and  in- 
dicates an  acid  auto-intoxication  and  an  insufficient  utilization 
of  carbohydrates.  In  the  experience  of  the  author,  acetone  may 
sometimes  be  found  in  the  saliva  when  it  cannot  be  found  in 
the  urine  (for  test,  see  Acetone  under  Saliva  and  Urine). 

Another  ketone  of  interest  is  laevulose,  fruit-sugar,  CH2OH- 
CHOH.CHOH.CHOH.CO.CH2OH,  which,  with  glucose,  will  be 
studied  later. 


ALCOHOLS  203 

While  the  oxidation  of  a  primary  alcohol  will  produce  an 
aldehyd  and  the  oxidation  of  a  secondary  alcohol  will  produce 
a  ketone,  the  tertiary  alcohol,  by  action  of  an  oxidizing  agent, 
is  spht  into  two  new  carbon  compounds,  that  is,  the  chain  is 
broken  and  simpler  ketones  and  acids  are  formed. 


CHAPTER  XXIII. 
ETHERS. 

Ethers  may  be  regarded  as  oxids  of  the  hydrocarbon  radi- 

C2H5  ^ 
cals,  as  O,  or  as  anhydrids  of    the  monatomic  alcohols, 

C2H5 
H2O  having  been  removed  from  two  molecules  of  the  alcohol: 

2C2H5OH-H2O   =    (C2H5)20. 

Ethers  may  be  simple,  mixed,  or  compound.  The  simple 
ether  is  illustrated  above  by  the  formula  for  ordinary  or  ethyl 
ether,  where  two  radicals  of  the  same  kind  are  united  by  an 
atom  of  oxygen. 

In  a  mixed  ether,  these  radicals  will  be  of  different  kinds; 
as,  for  example,  CH3-O-C2H5,  methyl-ethyl  ether. 

The  compound  ethers  are  compounds  of  alcohol  radicals 
with  acid  radicals,  that  is,  the  salts  of  alcohol  radicals.  The 
acid  may  be  either  organic  or  inorganic;  thus,  we  have  nitric 
ether,  ethyl  nitrate,  C2H5NO3,  and  we  have  acetic  ether,  ethyl 
acetate,  C2H5C2H3O2.  The  compound  ethers  are  often  called 
esters  and  form  a  large  and  important  class  of  organic  com- 
pounds. 

A  general  method  for  the  preparation  of  simple  and  mixed 
ethers  is  that  of  distillation  of  the  corresponding  alcohols  with 
sulphuric  acid,  as  illustrated  by  experiment  No.  69,  page  210. 
They  may  also  be  produced  by  the  action  of  silver  oxid  on  the 
corresponding  alkyl  iodids: 

2  C2H5I  +  Ag20  =   (C2H5)20  +  2  Agl, 

also,  by  treating  the  sodium  alcoholate  with  an  alkyl  iodid, 

204 


or 


ETHERS  205 

.CzHsONa  +  C2H5I  -  (C2H6)20  +  Nal 

CHsv 
CHsONa  +  C2H5I  =  O  +  Nal. 

C2H5 


Methyl  Ether.  —  Methyl  oxid,  (CH3)20,  also  known  as  formic 
ether,  is  isomeric  with  ordinary  alcohol,  and  may  be  made  in 
a  manner  similar  to  that  used  in  the  production  of  ethyl  ether 
{q.  v.).  At  ordinary  temperature  it  is  a  gas,  but  liquefies  at 
—  20°  C.  (Bernthsen).  It  has  been  used  as  a  general  anaesthetic, 
and  the  anaesthesia  is  said  to  be  profound  and  quickly  pro- 
duced (U.  S.  D.  from  A.  J.  P.,  Sept.,  1870). 

Methyl-ethyl  Ether.  —  This  name,  besides  indicating  a 
definite  compound  as  referred  to  in  the  preceding  paragraph, 
has  been  applied  to  a  mixture  of  methyl  ether  and  ethyl  ether, 
used  for  purposes  of  general  anaesthesia. 

Methylene  Ether.  —  A  name  applied  to  a  mixture  of  methyl- 
ene dichlorid  and  ethyl  ether,  used  as  an  anaesthetic,  but  it  has 
been  found  unsafe  (U.  S.  D.). 

Ethyl  Ether. —  Ethyl  oxid,  (C2H5)20,  consisting  of  96%  by 
weight  of  the  "aether"  of  the  pharmacopoeia  (the  other  4%  be- 
ing alcohol  and  a  little  water).  Ether  is  a  general  anaesthetic, 
widely  used!  It  is  made  by  the  action  of  sulphuric  acid  on 
ethyl  alcohol,  and  from  this  fact  has  been  known  as  sulphuric 
ether,  but  this  name  is,  of  course,  incorrectly  used,  sulphuric 
ether  being  properly  an  ethyl  sulphate  (02115)2804. 

In  the  preparation  of  ether,  sulphuric  acid  may  be  mixed  with 
rather  more  than  its  own  bulk  of  alcohol,  the  mixture  heated  to 
a  temperature  of  from  130°  to  138°  C.  in  a  suitable  retort  or 
still,  the  distillate  (ether)  being  collected  in  a  cold  receiver. 

The  reaction  takes  place  in  two  steps,  as  follows:  One  mole- 
cule of  acid  and  one  of  alcohol  react  to  form  ethyl  sulphuric 
acid  (ethyl  acid  sulphate)  and  H2O,  H2SO4  -|-  C2H5OII  = 
C2H5HSO4  4-  H2O.     Then  the  ethyl  sulphuric  acid  reacts  with 


2o6  ORGANIC  CHEMISTRY 

a  second  molecule  of  alcohol  to  form  ether  and  sulphuric  acid, 
C2H5HSO4  +  C2H5OH  =  (C2H5)20  +  H2SO4.  Thus  the  sul- 
phuric acid,  from  two  molecules  of  alcohol,  has  produced  one 
molecule  of  ether  and  is  in  condition  to  repeat  the  process,  hav- 
ing suffered  itself  only  to  the  extent  of  adulteration  with  one 
molecule  of  water.  In  accordance  with  this  theoretic  forma- 
tion of  ether  by  simple  dehydration  of  alcohol  by  H2SO4,  pro- 
vision is  made  for  a  continuous  process,  by  the  introduction  of  a 
constant  supply  of  fresh  alcohol  into  the  retort  during  the  dis- 
tillation, and  so  regulated  that  the  total  bulk  of  liquid  is  neither 
increased  nor  diminished.  The  product  is  then  purified,  and 
freed  from  water  and  traces  of  acid  by  redistillation  over  a  mix- 
ture of  lime  and  calcium  chlorid. 

Ether,  according  to  the  U.  S.  P.  requirements,  is  "  a  trans- 
parent, colorless,  mobile  liquid  with  characteristic  odor  and 
a  burning  and  sweetish  taste";  specific  gravity  of  0.725  to  0.728 
at  15°  C.  and  boiling  at  about  37°  C.  It  is  readily  inflam- 
mable, and  this  fact,  together  with  its  easy  volatility,  makes 
it  necessary  to  use  considerable  care  when  handling  it. 
Absolute  ether  boils  between  34°  and  35°  C. 

The  action  of  sulphuric  acid  upon  alcohol  needs  careful 
regulation;  because  there  may  be  produced  three  other  products 
in  addition  to  the  ethyl  oxid  already  considered.  These  are, 
first,  ethyl  sulphuric  acid,  C2II5HSO4;  second,  ethyl  sulphate 
(02115)2804,  these  being  respectively  the  acid  and  neutral  ethyl 
esters  of  H2SO4;  third,  the  hydrocarbon  ethylene,  C2H4. 
This  latter  compound  is  the  first  of  the  ethylene  series  of 
hydrocarbons  with   the  general   formula    CnH2n,  and  contain- 

Hx  /H 

ing  "double-bonded"   carbon  atoms,        C  =  C         or  CH2  = 

CII.CH3.  These  are  unsaturated  hydrocarbons  (see  page  189). 
Ethylene  is  produced  by  the  action  of  an  excess  of  concentrated 
H2SO4,  which  abstracts  H2O   from  each  molecule   of   alcohol 


ETHERS  207 

(C2H5OH— H20  =  C2H4),  whereas  in  the  preparation  of  ether  the 
more  dilute  acid  abstracts  H2O  from  two  C2H5OH. 

Compound  Ethers  or  Esters. 

One  of  the  most  important  of  this  class  of  compounds,  from 
a  dental  standpoint,  is  the  benzoyl-ecgonine   methyl  ester   or 

(C5H7 
cocain,  CH3N  <   |  While  of  considera- 

(  CH.C7H5O2.CH2.CO2CH3 

ble  interest,  the  elucidation  of  the  exact  chemical  relationship  of 
this  compound  to  tropa-cocain,  etc.,  is  beyond  the  scope  of  this 
work. 

Another  methyl  ester  of  much  simpler  chemical  composition 
is  methyl  salicylate,  CH4-CH-COOCH3. 

Salicylic  acid  is  CH4-OH-COOH  (oxybenzoic  acid),  and 
its  methyl  ester  constitutes  the  methyl  salicylate  of  the  U.  S.  P. 
It  is  identical  with  the  volatile  oil  of  betula  and  with  90% 
of  the  oil  of  gaultheria  (wintergreen) .  This  latter  oil  is  much 
used  as  a  flavor  in  dental  preparations,  tooth-washes,  powders, 
etc. 

Ethyl  Acetate,  CH3-COO.C2H5,  is  formed  by  heating  ethyl 
alcohol,  sulphuric  acid,  and  acetate  of  sodium.  This  reaction 
constitutes  a  qualitative  test  for  acetic  acid  or  acetates,  the 
odor  of  the  ester  being  sufficiently  characteristic  to  furnish 
a  delicate  test  (page  94). 

The  acetic  ether  of  the  U.  S.  P.  is  "a  Hquid  composed  of 
about  98.5%  of  ethyl  acetate  and  1.5%  alcohol." 

Ethyl  Butyrate,  CH3-CH2-CH2-COOC2H5.  This  ester  dis- 
solved in  10  parts  of  alcohol  forms  pineapple  essence.  It 
may  be  made  in  a  manner  similar  to  the  preparation  of  ethyl 
acetate,  i.e.,  by  heating  together  alcohol,  butyric  acid,  and 
concentrated  sulphuric  acid.  The  production  of  the  ester  is 
Hkewise  used  as  a  quahtative  test  for  the  presence  of  the  acid, 
and  employed  in  the  examination  of  gastric  contents  as  follows: 


2o8  ORGANIC   CHEMISTRY 

"Heat  lo  c.c.  of  contents  with  5  ex.  of  strong  sulphuric  acid 
and  4  c.c  of  95%  alcohol:  odor  of  pineapple  indicates  butyric 
acid."     (Hewes.) 

Ethyl  Nitrite,  C2H5NO2,  may  be  made  by  heating  sodium 
nitrite  with  concentrated  sulphuric  acid  and  alcohol,  also  by 
the  reduction  of  nitric  acid  by  copper  in  presence  of  alcohol 
and  sulphuric  acid.  The  ethyl  nitrite  is  distilled,  and  must 
be  collected  in  a  receiver  surrounded  by  a  freezing  mixture  of 
ice  and  salt.  Pure  ethyl  nitrite  boils  at  18°  C,  and  has  a  gravity 
of  0.900.  An  alcoholic  solution  constitutes  sweet  spirits  of 
nitre,  the  spiritus  aetheris  nitrosi  of  the  U.  S.  P. 

This  preparation  should,  according  to  Dr.  E.  R.  Squibb, 
contain  4.5%  ethyl  nitrite. 

Amyl  Acetate  and  Amyl  Butyrate  may  be  obtained  by  heat- 
ing the  respective  acids  with  amyl  alcohol  (C5H11OH)  and  strong 
sulphuric  acid.  These  esters  may  also  be  used  in  detecting  the 
presence  of  the  acid,  amyl  alcohol  being  used  in  place  of  ordinary 
alcohol.  Amyl  acetate  gives  the  odor  of  pears,  amyl  butyrate 
that  of  bananas. 

Amyl  nitrite,  C5H11NO2,  is  a  compound  used  in  medicine  to  a 
considerable  extent,  usually  administered  by  inhalation.  The 
U.  S.  P.  preparation  contains  about  80%  of  amyl  nitrite.  It  is 
very  soluble  and  inflammable. 

The  Fats  are  esters  of  glyceryl,  C3H5,  also  called  tritenyl, 
propenyl,  etc.  This  radical  forms  with  hydroxyl  (OH)  the  pro- 
penyl  alcohol,  C3H5(OH)3,  which  is  ordinary  glycerin  or  glycerol. 

Glyceryl  butyrate  or  butyrin,  CH3-(CH2)2-COOC3H5,  con- 
stitutes (together  with  smaller  quantities  of  the  glyceryl  esters 
of  capric,  caproic,  and  capryUc  acids)  about  7%  of  butterfat. 
These  esters  are  readily  saponified  by  treatment  with  alcohoHc 
potash;  then,  by  decomposition  of  the  potassium  salts  with 
H2SO4,  the  acids,  being  volatile,  may  be  separated  by  distillation. 
The  amount  of  volatile  fat  acids  thus  obtained  is  a  valuable  test 
for  the  genuineness  of  the  butter. 


ETHERS  209 

Glyceryl  Palmitate,  C3H5(Ci6H3i02)3,  tripalmitin ;  glyceryl 
stearate,  C3H5(Ci8H3502)3,  tristearin,  and  glyceryl  oleate, 
C3H5(Ci8H3302)3,  triolein;  these  in  varying  proportions  make  up 
the  greater  part  of  animal  and  vegetable  fats  and  oils. 

The  prefix  "tri"  is  used  because  the  "mono"  and  "di" 
compounds,  as  monopalmitin,  C3H5(OH)2-Ci6H3i02,  etc.,  are 
possible  and  may  be  prepared  by  synthesis.  Triolein  is  liquid 
at  ordinary  temperature,  solidifies  at  -6°  C,  is  a  "double- 
bonded"  compound,  hence  forms  addition-products  with  the 
halogens  as  stearin  and  palmitin  cannot  do,  they  being  "satu- 
rated hydrocarbons. " 

The  amount  of  chlorin  or  bromin  which  a  fat  or  oil  can  thus 
absorb  is  an  index  of  the  proportion  of  unsaturated  fatty  acids 
contained  in  it,  and  hence  becomes  a  valuable  method  of 
identification.  Olive-oil  and  lard-oil  contain  large  amounts  of 
olein. 

Tripalmitin  melts  at  66°  C,  is  usually  obtained  from  palm- 
oil.  Tristearin  melts  at  72°  C,  occurs  with  palmitin  and  olein 
in  beef -fat,  mutton- tallow,  etc.,  the  consistence  of  the  fat  being 
dependent  upon  the  proportions  of  the  constituent  esters. 

The  fats,  stearin  for  example,  may  be  split  into  glycerol  and 
fatty  acid  by  steam  under  pressure  as  follows : 

C3H5(Ci8H3502)3  +  3  H2O   =   C3H5(OH)3  +  3  HC18H35O2. 

A  partial   result  of    this    sort  is    brought    about   by  the    fat- 
spKtting  enzyme  (lipase)  of  the  pancreatic  juice  (see  Steapsin). 
Saponification  of  the  fats  by  caustic  alkali  takes  place  as 
follows : 

C3H5(Ci8H3502)3  +  3  KOH  =   C3H5(OH)3  +  3  KCX8H35O2. 

The  potassium  salts  of  the  fatty  acids  constitute  the  soft 
soaps,  while  the  sodium  salts  are  in  general  the  hard  soaps. 
The  "salting-out"  process  in  soap  manufacture  brings  about 
a  double  decomposition  resulting  in  the  production  of  ordinary 
soap. 


2IO  ORGANIC  CHEMISTRY 

Laboeatory  Exercise  LIV, 
Experiments  with  Acetone  and  Ethers. 

Exp.  65.  Preparation  of  Acetone:  Heat  a  few  grams  of 
dried  calcium  acetate  in  an  ignition  tube,  collect  the  distillate, 
which  consists  of  an  impure  acetone.  If  this  is  mixed  with  a 
little  water  and  filtered,  part  of  the  impurities  may  be  removed, 
and  the  filtrate  tested  for  acetone  by  the  following  experiment. 

Exp.  66.  Dilute  the  filtrate  from  the  last  experiment  with 
distilled  water;  add  a  crystal  of  potassium  nitroprussid.  After 
the  crystal  is  dissolved,  add  a  few  drops  of  acetic  acid,  and  then 
an  excess  of  ammonia  water.  A  violet  or  purple  color  indicates 
the  presence  of  acetone.  Using  a  dilute  solution  of  acetone  in 
place  of  the  alcohol  in  experiment  57,  on  page  194,  produce  iodo- 
form crystals  by  similar  reaction  with  iodin  and  sodium  or  po- 
tassium carbonate. 

Exp.  67.  Acetone  may  be  dissolved  or  mixed  with  water  in 
all  proportions;  but,  upon  saturating  the  water  with  KOH, 
the  acetone  will  form  a  separate  layer  which  may  be  drawn  off  as 
in  the  separation  of  alcohol  in  experiment  59,  page  200. 

Exp.  68.  To  a  dilute  aqueous  solution  of  acetone  add 
potassium  permanganate  slowly  until  the  mixture  is  perma- 
nently colored  pink;  filter,  add  dilute  sulphuric  acid  and  distil 
until  I  or  2  c.c.  of  distillate  are  obtained.  This  may  be  tested 
for  acetic  acid  by  Htmus  paper  or  ferric  chlorid. 

Exp.  69.  Into  a  large  test-tube  put  a  little  alcohol  and  about 
half  its  volume  of  strong  H2SO4.  Warm  gently  and  notice  the 
odor. 

Ether  is  formed  by  two  reactions.  First,  C2H5OH  +  H2SO4 
=  C2H5IISO4  +  H2P.  Then  the  ethyl-hydrogen  sulphate 
(C2II5HSO4)  is  acted  upon  by  a  second  molecule  of  H2SO4,  as 
foUows:  C2H5HSO4  +  C2H5OH  =  (C2H5)20  +  H2SO4. 

Exp.  70.  The  production  of  compound  ethers  may  be  dem- 
onstrated by  the  test  for  acetic  acid  forming  ethyl  acetate, 


ETHERS  211 

page  94,  or  by  the  following  experiment  used  to  detect  butyric 
acid  in  gastric  contents: 

Exp.  71.  Mix  in  a  test-tube  5  c.c.  of  a  dilute  (1/2%)  solu- 
tion of  butyric  acid  with  an  equal  volume  of  strong  H2SO4  and 
as  much  strong  alcohol.  Heat  gently  and  note  the  odor  of 
ethylbutyrate  (pineapples) . 

Exp.  72.  To  about  5  c.c.  of  an  aqueous  solution  of  chloral 
hydrate  add  a  few  cubic  centimeters  of  strong  NaOH  solution 
and  boil.     Note  odor  of  chloroform. 

Exp.  73.  Isobenzonitril  test  for  chloral  or  chloroform: 
Place  a  few  drops  of  a  dilute  chloral  hydrate  solution  (or  a 
small  drop  of  chloroform)  in  a  test-tube,  add  5  c.c.  of  an  alco- 
holic solution  of  alkali  hydrate  *  (NaOH  or  KOH)  and  one  drop 
only  of  fresh  aniline  oil.  Heat  till  the  mixture  just  begins  to 
boil  and  note  the  odor  of  the  nitril. 

*  If  alcoholic  potash  or  soda  is  not  at  hand,  the  test  may  be  performed  with 
5  c.c.  of  alcohol  and  i  or  2  c.c.  of  a  40%  aqueous  solution  of  NaOH. 


CHAPTER  XXIV. 

ORGANIC   ACIDS. 

If  the  oxidation  of  an  alcohol  is  carried  beyond  the  formation 
of  aldehyd  or  ketone,  i.e.,  if  the  aldehyd  or  ketone  be  oxidized, 
an  organic  acid  results.  The  first  atom  of  oxygen  involved 
in  this  process  does  not  become  a  constituent  part  of  the  new 
molecule,  but  simply  withdraws  hydrogen  from  the  old  (the 
alcohol),  as  shown  in  the  formation  of  aldehyds  on  page  198. 
The  second  atom  of  oxygen,  however,  attaches  itself  to  the 
molecule  and  does  become  a  part  of  the  new  substance  (the  acid) : 

CH3  CH3  CH3  CHa 

I        +0=1      +H2O        I       +0=1 
CH2OH         CHO  CHO  COOH 

Alcohol.  Aldehyd.  Aldehyd.  Acid. 

The  group  -COOH  is  known  as  carboxyl  and  is  the  char- 
acteristic grouping  of  the  acids.  The  H  of  the  carboxyl  differs 
from  the  other  atoms  of  H  in  the  molecule  in  that  it  is  united 
to  oxygen  rather  than  to  carbon,  and  constitutes  the  basic  or 
replaceable  H  of  the  acid;  hence  acetic  acid  is  monobasic,  and 
the  only  possible  salt,  of  potassium,  for  instance,  is  CH3-COOK. 

The  basicity  of  the  acid  depends  on  the  number  of  carboxyl 
groups  it  contains. 

Among  the  monobasic  acids  of  the  fatty  or  parajQSn  series 
which  we  will  study  are  the  following: 

Representative  Fatty  Acids. 

H.COOH  =  formic  acid  or  hydrogen  formate; 
CH3.COOH  =  acetic  acid  or  hydrogen  acetate; 
C2H5.COOH  =  propionic  acid  or  hydrogen  propionate; 


ORGANIC  ACIDS  213 

C3H7COOH  =  butyric  acid  or  hydrogen  butyrate; 

C4H9COOH  =  valeric  acid  or  hydrogen  valerate; 
C15H31COOH  =  palmitic  acid  or  hydrogen  palmitate; 
C17H35COOH  =  Stearic  acid  or  hydrogen  stearate. 

The  acids  of  these  series  are  represented  by  the  general 
formula  CiiH2n02.  They  are  all  monobasic;  i.e.,  they  contain 
only  one  atom  of  replaceable  hydrogen. 

Formic  Acid,  (H.COOH),  originally  distilled  from  the  bodies- 
of  ants  (formica,  from  which  the  name  is  derived),  is  a  colorless, 
easily  volatile  Hquid.  It  may  be  prepared  in  the  laboratory 
by  heating  oxaHc  acid  with  glycerol,  when  the  oxalic  acid  breaks 
up  into  formic  acid  and  CO2, 

C2H2O4  =  CO2  +  HCOOH. 

Carbon  monoxid,  passed  over  hot  KOH,  results  in  the  forma- 
tion of  potassium  formate, 

CO  +  KOH  =  HCOOK. 

Also  by  treatment  of  ammonium  carbonate  with  nascent  hydro- 
gen (sodium  amalgam) , 

C03(NH4)2  +  2  H  =  HC00(NH4)  +  H2O  -f  NH3), 
and 

HC00(NH4)  -F  NaOH  =  HCOONa  -f  NH3  +  H2O. 

Formic  acid,  according  to  the  above  reaction,  is  apparently 
carbonic  acid  less  one  atom  of  oxygen,  and  the  fact  that  formic 
acid  acts  easily  as  a  reducing  agent,  taking  away  oxygen  from 
other  bodies  and  becoming  H2CO3,  is  further  proof  of  this 
relationship. 

Acetic  Acid,  CH3COOH,  is  obtained  commerciaHy  by  the 
oxidation  of  ethyl  alcohol.  It  is  the  acid  of  vinegar,  which, 
according  to  Massachusetts  law,  should  contain  4^%  of  acid. 
Glacial  acetic  acid  is  a  commercial  name  of  the  acid  contain- 
ing 1%  or  less  of  water:  it  is  a  colorless  soHd  at  a  temperature 
below  15°  C.  The  U.  S.  P.  acetic  acid  contains  only  36%  (by 
weight)  of  the  pure  acid. 


214  ORGANIC  CHEMISTRY 

Either  one,  two,  or  all  three  of  the  hydrogen  atoms  of  the 
CH3  group  may  be  replaced  by  chlorin,  forming  respectively 
the  mono-,  di-,  and  tri-chloracetic  acids,  the  trichloracetic  acid 
being  used  to  a  considerable  extent  in  dentistry  (page  1 76) . 

Acetic  acid,  by  the  abstraction  of  water,  forms  an  anhydrid, 
C4H6O3: 

2  HC2H3O2   =   (C2H30)20  +  H2O. 

This  substance  is  of  considerable  inportance  in  organic  reac- 
tions. It  is  a  colorless  liquid  with  a  boihng-point  of  138°  C, 
and,  with  the  halogens,  forms  compounds  such  as  acetyl  chlorid, 
C2H3OCI,  the  radical  C2H3O  being  known  as  the  acetyl  radical. 

Propionic  acid,  CH3.CH2.COOH,  is  a  colorless  liquid, 
boiling  at  140°  C.  According  to  Witthaus,  it  is  best  prepared 
by  heating  ethyl  cyanid  with  caustic  potash  until  the  odor  of  the 
ester  has  disappeared: 

C2H5CN  -f  KOH  +  H2O  =  C2H5COOK  -f  NH3. 

Then,  by  treatment  with  H2SO4,  the  propionic  acid  is  liberated, 
and  may  be  separated  by  distillation. 

Butjrric  Acid,  C3H7COOH,  occurs  as  a  product  of  fermenta- 
tion of  butter,  or  other  animal  fat  containing  butyrin;  also 
from  the  decomposition  of  lactic  acid,  two  molecules  of  lactic 
acid  furnishing  one  of  butyric  acid,  2  CO2  and  2  H2.  It  is  an 
occasional  constituent  of  the  gastric  contents,  and  may  be 
detected  by  formation  of  the  ethyl  ester  (page  207).  The  pure 
acid  is  a  heavy,  colorless  Hquid  with  characteristic  odor,  soluble 
in  II2O  in  any  proportion.  See  page  208  for  the  glyceryl  ester 
of  butyric  acid  (butyrin) ;  also  for  stearic  and  palmitic  acids. 

Valeric  Acid,  C4H9COOH,  may  be  made  by  the  oxidation  of 
amyl  alcohol  (C5H11OH).  It  is  an  oily  Hquid  boiling  at  174°  C. 
It  occurs  as  a  constituent  of  valerian,  and  in  consequence  has 
been  called  valeric  acid.  Its  salts  are  used  in  medicine  as  seda- 
tives. 


ORGANIC  ACIDS  215 

The  valeriate  of  amyl  has  an  odor  resembhng  that  of  apples, 
and  is  used  in  alcoholic  solutions  as  apple  essence. 

Palmitic  Acid,  C15H31COOH,  a  sohd  "fat  acid,"  occurs  as  a 
glyceryl  ester  in  butter  (to  a  very  sHght  extent),  in  oHve  oil, 
palm  oil,  and  bayberry  wax.  Combined  with  certain  alcohols  it 
occurs  in  white  and  yellow  wax;  also  in  spermaceti. 

Palmitin,  C3H5(Ci6H3i02)3,  occurs  in  all  animal  fat  and  in 
large  quantities  in  human  fat. 

Stearic  Acid,  Ci8H35COOH[CH3-(CH2)i6-COOH],  as  glyceryl 
stearate  or  stearin  occurs  in  vegetable  and  animal  fats,  particu- 
larly in  tallow.  Stearic  acid  is  only  slightly  soluble  in  alcohol 
or  in  ether.     Its  melting-point  is  69.3°  C. 

Laboratory   Exercise  LV. 
Experiments  with  organic  acids.     (CnH2ii02). 

Exp,  74  and  75.  Experiments  70  and  71  may  be  used  as  il- 
lustrating the  laboratory  test  for  acetic  and  butyric  acids.  In 
addition  a  test  for  lactic  acid  may  be  made  with  the  ferric  chlorid 
test,  which  is  also  applicable  to  gastric  contents.  Exp.  91, 
page  225. 

Exp.  76.  Introduce  into  a  small  flask  (250  c.c.  capacity) 
about  30  c.c.  of  anhydrous  glycerin  and  an  equal  weight  of 
oxalic  acid  crystals.  Boil  for  several  minutes;  CO2  is  given 
off  and  a  compound  formed  between  the  acid  and  glycerin; 
then,  upon  addition  of  more  acid  and  continued  heating,  formic 
acid  may  be  distilled.  Collect  about  10  c.c.  of  distillate;  test 
reaction  with  litmus-paper.  Make  silver-mirror  test,  described 
on  page  201,  Exp.  64.  The  silver  solution  will  be  reduced,  but 
difficulty  will  be  experienced  in  obtaining  the  mirror. 

Exp.  77.  To  5  c.c.  of  formic  acid  solution  add  2  or  3  c.c.  of 
dilute  H2SO4  (1-5)  and  a  little  potassium  permanganate  solu- 
tion; heat  the  mixture  and  conduct  the  gas  evolved  into  a 
tube  containing  lime  water. 

Exp.  78.     From  a  mixture  of  formic  acid,  alcohol,  and  sul- 


2l6  ORGANIC  CHEMISTRY 

phuric  acid,  ethyl  formate  may  be  evolved  in  a  manner  similar 
to  that  in  the  production  of  ethyl  acetate  (page  95).  Compare 
the  odors  of  these  two  ethers. 

Exp.  79.  To  a  dilute  solution  of  ferric  chlorid  add  a  little 
acetic  acid;  divide  the  solution  into  two  parts;  to  one  add  mer- 
curic chlorid  and  to  the  other  HCl,  and  note  results. 

Exp.  80.  Repeat  Exp.  79,  using  diacetic  acid  in  place  of 
acetic. 

Exp.  81.  Repeat  Exp.  79  using  meconic  acid*  in  place  of 
acetic. 

Compare  results  of  these  three  experiments  and  save  record 
for  future  use  in  the  study  of  saliva. 

Exp.  82.  In  a  small  flask  saponify  a  little  butter  by  heating 
with  alcoholic  potash  over  a  steam  bath  till  mixture  is  dry. 
Dissolve  in  water,  add  dilute  H2SO4,  and  distil  off  a  portion  of 
the  butyric  acid.  Record  whatever  can  be  learned  from  this 
experiment  regarding  the  physical  properties  of  the  butyric 
acid. 

Exp.  83.  Take  about  5  c.c.  each  of  alcoholic  solution  of 
stearic  and  oleic  acids  and  treat  separately  with  about  i  c.c.  of 
1%  iodin  solution  (alcoholic) ;  allow  to  stand  for  some  time,  and 
explain  fully  the  difference  in  action  exhibited  by  the  two  fatty 
acids. 

Acrylic  Acid  Series. 

Acrylic  acid,  CH2:  CH.COOH,  is  a  type  of  the  double- 
bonded  acids.  It  is  a  liquid  with  boiling-poiijt  at  140°  C.  Nas- 
cent hydrogen  breaks  the  double  bond,  forming  propionic  acid, 
CH3.CH2.COOH.  HI  will  also  break  the  double  bond  by 
direct  union  of  its  constituents,  forming  CH2I-CH2-COOH, 
(iS-iodo  propionic  acid). 

Acrylic  aldehyd,  or  acrolein,  is  a  colorless  liquid  boiling  at 
52°  C.     Its  vapor  has  an  irritating,  pungent  odor,  sufficiently 

*  Laudanum  diluted  with  water  till  color  is  light  brown  may  be  used. 


ORGANIC  ACIDS  217 

characteristic  to  be  used  as  a  qualitative  test  for  glycerol,  from 
which  it  is  obtained  by  heating  with  KHSO4. 

The  only  other  acid  of  particular  importance  in  this  series  is 
oleic  acid,  C17H33COOH.  It  is  an  important  constituent  of  oils, 
both  animal  and  vegetable,  and  consists,  to  a  great  extent,  of 
such  substances  as  lard  oil,  cotton  seed  oil,  etc. 

Dibasic  Acids. 

COOH   COOH     COOH 
I        I         I 
COOH   CH2      CH2 


Oxalic  acid. 


I  I 

COOH  CH2 

Malonic  acid.  1 

COOH 

Succinic  acid. 

Dibasic  acids  contain  two  carboxyl  groups.     These  are  refer- 
able to,  and  in  many  cases  may  be  formed  from,  the  diatomic 

CH2OH 
alcohols.     Thus  glycol,    I  ,  upon  oxidation  yields  glycolHc 

CH2OH 
CH2OH  COOH 

acid,    I  ,  and  oxalic  acid,   I 

COOH  COOH 

/OH 
Carbonic  acid,  O  =  C  ,  is  dibasic  in  that  it  contains  two 

^OH 
atoms  of  replaceable  hydrogen,  though  not  two  carboxyl  groups. 
It  is  claimed  that  a  molecule  of  this  sort  cannot  exist  because 
a  single  carbon  atom  cannot  hold  more  than  one  hydroxyl  group 
in  combination.  This  acid  has  never  been  isolated,  all  attempts 
to  separate  it  in  the  pure  form  resulting  in  the  formation  of 
carbonic  acid  gas  and  water.  Its  compounds  (carbonates)  are 
very  common  and  very  important,  both  in  organic  and  inorganic 
chemistry.  Organic  salts  of  carbonic  acid  may  be  made  by 
treating  silver  carbonate  with  alkyl  iodid. 


2l8  ORGANIC  CHEMISTRY 

,OAg  /OC2H5 

CO  +  2  C2H5I  =  CO  +2  Agl. 

^OAg  ^OCsHs 

Oxalic  Acid,  which  may  be  considered  as  a  type  of  the  di- 
basic acids,  occurs  as  small,  colorless  crystals  (four-  or  six-sided 
prisms),  containing  two  molecules  of  water  of  crystallization 
(H2C2O4.2  H2O);  it  is  but  slightly  efflorescent,  and,  if  carefully 
crystallized,  is  suitable  for  the  preparation  of  standard  acid 
solution.  Salts  of  oxalic  acid  occur  in  many  plants;  the  acid 
potassium  oxalate,  "salt  of  sorrel,"  is  found  in  common  red 
sorrel  (Rumex  acetora)  and  in  wood  sorrel  (Oxalis  acetocella). 
Oxalic  acid  in  various  combinations,  often  with  lime,  is  widely 
distributed  in  articles  of  vegetable  diet,  particularly  tomatoes, 
rhubarb,  spinach,  and  asparagus;  grapes,  apples,  and  cabbages 
also  carry  oxalates,  but  in  smaller  amounts. 

The  source  of  oxalates  in  the  system  is  twofold,  —  the  in- 
gested oxalates  and  those  produced  by  oxidation,  incident  to 
metabolism,  the  exact  nature  of  which  has  not  been  clearly 
demonstrated  (see  Calcium  and  Sodium  Oxalates,  under  Urine 
and  Saliva). 

Oxalic  acid  was  previously  made  commercially  by  the  action 
of  strong  nitric  acid  on  starch  or  sugar;  it  is  now  prepared  by 
heating  cellulose  (in  form  of  sawdust)  with  a  mixture  of  KOH 
and  NaOH,  precipitating  the  acid  as  CaC204,  and  decomposing 
the  salt  by  H2SO4.  The  acid  is  then  purified  by  repeated 
crystallization. 

Malonic  Acid,  COOH-CH2-COOH,  is  an  oxidation  product 
of  malic  acid  (from  apples),  and  is  comparatively  unimportant. 

Succinic  Acid,  COOH(CH2)2-COOH,  occurs  in  amber,  from 
which  it  takes  its  name  (Amber-Succinum) .  It  has  been  de- 
tected in  the  urine  after  asparagus  and  some  fruits  have  been 
eaten.  It  occurs  as  colorless  crystals,  soluble  in  water,  and  only 
sHghtly  soluble  in  ether.  Succinic  acid  may  be  obtained  by  the 
saponification  of  ethylene  cyanid,  C2ll4(CN)2,  and  is  a  dibasic 


ORGANIC  ACIDS  219 

acid  containing  four  carbon  atoms.  It  is  a  constituent  of  some 
transudates  and  cyst  fluids.  It  occurs  in  the  spleen  and  thyroid 
gland,  and  has  been  found  in  sweat  and  in  the  urine  (Ham- 
marsten) . 

Pyro-tartaric  Acid,  formed  by  the  distillation'of  ordinary  tar- 
taric acid,  is  one  of  four  isomers  of  formula  C5II8O4,  and  is  of 
interest  only  in  its  relation  to  some  of  the  amino  acids  which 
result  from  protein  digestion.  Formula  for  pyro-tartaric  acid 
is  CH3-CHCOOH-CH2-COOH. 

Oxy  acids. 

Hydroxy  acids,  or  alcohol  acids,  contain  hydroxyl  in  place 
of  one  or  more  hydrogen  atoms  of  the  fatty  acids.  Thus  we 
may  consider 

Carbonic  acid  as  hydroxyformic  acid,  HO-COOH; 

CH2OH 
Glycohc  acid  as  hydroxy  acetic  acid,    I  ; 

COOH 

C2H4OH 

Lactic  acid  as  hydroxypropionic  acid,   I  ; 

COOH 

Mahc  acid  (from  apples)  as  hydroxy-  CHOH-COOH 
succinic  acid,  CH2-COOH 

Tartaric    acid   is   dihydroxysuccinic  ™^^"^^^^ 
acid,  CHOH-COOH 

Citric  Acid,  from  lemons,  limes,  etc.,  is  in  a  class  by  itself. 
It  is  a  tribasic  acid  (has  three  carboxyl  groups  and  one  hydroxyl) ; 
the  formula  is  C3H40H-(COOH)3. 

Glycollic  Acid  occurs  in  nature  in  unripe  grapes,  and  possibly 
as  antecedent  to  oxalates  in  the  system  (Dakin,  Journal  of  Biol. 
Chem.,  3.57).  Glycolhc  acid  is  formed  from  glycol  by  oxidation, 
and  from  glycocoll,  by  action  of  nitrous  acid. 


2  20  ORGANIC  CHEMISTRY 

Nitric  acid  will  oxidize  gly collie  acid  to  oxalic  acid. 

Lactic  Acid.  —  Oxypropionic  acid,  or  i  *  -ethylidene  lactic 
acid,  CH3-CHOH-COOH,  is  ordinary  lactic  acid  produced  by 
fermentation  of  milk-sugar,  etc.  It  occurs  in  the  gastric  juice 
and  in  contents  of  the  intestine,  "particularly  during  a  diet 
rich  in  carbohydrates,"  possibly  in  muscle  and  brain  tissue 
(Foster).     It  is  not  volatilized  at  temperature  below  160°  C. 

Sarcolactic  or  paralactic  acid,  df-ethylidene  lactic  acid, 
occurs  in  meat  extract.  The  presence  of  this  acid  causes  the 
acid  reaction  of  dead  muscle,  possibly  of  contracted  muscle. 
It  occurs  in  the  blood  and  at  times  in  the  urine,  and  it  is  probable 
that  it  is  this  modification  that  may  be  found  as  lactates  and 
acid  lactates  in  the  saliva  and  urine,  the  crystalline  forms  of 
which  have  been  identified  by  Dr.  E.  C.  Kirk  of  Philadelphia, 
by  the  use  of  the  micropolariscopic  method  of  Dr.  Joseph  P. 
Michaels  of  Paris.  This  statement  as  yet  lacks  confirmatory 
demonstration. 

Both  of  these  acids  form  characteristic  crystalline  salts  of 
zinc  and  of  calcium.  In  cold  water  the  zinc  sarcolactate  is 
more  soluble  than  zinc  lactate;  on  the  other  hand,  the  calcium 
sarcolactate  is  rather  less  soluble  than  calcium  lactate. 

p-Oxybutyric  Acid,  CH3-CHOH-CH2-COOH.  If  there  is 
introduced  into  butyric  acid,  CH3-CII2-CH2-COOH,  an  OH 
group,  an  oxybutyric  results.  If  this  alcohol  group  (OH) 
occupies  the  secondary  or  /3  position  (i.e.,  attached  to  the  carbon 
atom  twice  removed  from  the  carboxyl),  the  acid  is  the  /3-oxy- 
butyric  as  above. 

By  oxidation  of  the  compound,  the  alcohol  group  is  broken 
up  and  H  withdrawn  to  form  water,  leaving  a  keto  acid, 
CH3-CO-CH2-COOH,  known  as  diacetic  acid.  This  in  turn 
may  give  off  carbon  dioxid  and  become  dimethyl  ketone,  or 
acetone,  CH3-CO-CH3.  These  three  substances,  /3-oxybutyric 
acid,  diacetic  acid,  and  acetone,  are  classed  in  von  Noorden's 

*  Optically  inactive.  t  Dextrorotary. 


ORGANIC  ACIDS  221 

"  Autointoxication,"  and  in  the  works  of  other  recent  writers, 
as  ''the  acetone  bodies,"  and  by  this  convenient  term  we  may 
refer  to  them  collectively.  They  occur  in  diabetic  urine  and, 
according  to  von  Noorden,  in  other  cases  of  perverted  oxidation 
(not  insufhcient  oxidation). 

Tartaric  Acid  is  a  dihydroxysuccinic  acid,  C00H-(CH0H)2- 
COOH,  obtained  from  grape-juice.  The  double  tartrate  of 
sodium  and  potassium  (Rochelle  salt),  KNaC4H406,  is  much 
used  in  medicine. 

Tartaric  acid  combines  with  potassium  and  antimony  to 
form  tartar  emetic,  (KSbOC4H406)2H20. 

The  "scale  salts  of  iron,''  "ferri  et  ammonii  tartras"  and 
*'ferri  et  potassii  tartras,"  are  prepared  by  dissolving  freshly 
precipitated  ferric  hydroxid  in  the  acid  tartrate  of  ammonia  or 
potash,  and,  after  evaporation  to  thick  syrup,  sohdifying  in 
thin  layers  on  glass  plates. 

Potassium  Bitartrate,  or  acid  tartrate,  KHC4H4O6,  is  cream 
of  tartar,  and  one  of  the  few  salts  of  potassium,  only  sparingly 
soluble  in  water.     Its  commercial  source  is  the  wine-vat. 

Monobasic  Amino  Acids. 
Amino  acids,  formerly  called  amido  acids,  are  characterized 
by  an  NH2  group  in  place  of  H-;   for  example,  acetic  acid  is 

CH3  CH2NH2 

1  Amino  acetic  acid  is  I  .    These  acids  are  of  par- 

COOH  COOH 

ticular  interest  because  of   their  close  relationship  to  protein, 
many  of   them  being  among  the  cleavage  products  of  protein 

hydrolysis. 

That  many  of  the  amino  acids  are  formed  as  intermediate 
steps  in  the  reduction  of  the  complex  protein  molecules  to  urea 

is  certain. 

A  faulty  metaboHsm,  which  stops  short  of  normal  oxidations, 


222  ORGANIC  CHEMISTRY 

results  in  throwing  these  amino  acids  off  in  the  urine  or  faeces 
and  their  presence  indicates  abnormal  conditions  of  one  sort 
or  another. 

NH2 
Amino  formic  or  carbamic  acid,     I  ,  is  a  hypothetical 

COOH 
acid  which  would  consist  simply  of  an  amino  group,  NH2,  united 
to  a  carboxyl  group,  COOH.     By  the  union  of  ammonia  and 
carbon  dioxid  the  ammonium  salt  of  this  acid  is  formed, 

NH2 

.  2  NH3  +  CO2  =  I 

COONH4 

Ammonium  carbamate,  is  a  constituent  of  commercial  ammo- 
nium carbonate  and  an  antecedent  of  ammonium  carbonate  in 
the  hydrolysis  of  urea. 

Amino-acetic  Acid,  also  called  glycocoll  and  glycin,  is  obtained 
with  other  amino  acids  by  boiling  glue  with  either  acids  or 
alkalis.*  It  is  also  obtained,  by  the  hydrolysis  of  glycocholic 
acid,  from  bile. 

Hippuric  Acid  (Plate  V,  Fig.  4)  consists  of  benzoic  acid 
united  chemically  to  glycocoll,  and  may  be  produced  syntheti- 
cally by  the  union  of  these  two  substances. 

Amino-valeric  Acid,  CH2(NH2)-(CH2)3-COOH,  may  be  ob- 
tained with  glycocoll  from  elastin,  the  protein  of  the  elastic 
fibres,  of  tendons,  etc.j  Isomeric  with  amino-caproic  acid  is 
leucin,  an  amino-isobutyl-acetic  acid,  J 

CH3- 

CH-CH2-CH(NH2)-COOH. 
CHs^ 

Leucin  is  a  cleavage  product  in  the  decomposition  of  proteins, 
including   keratin    and    collagen.     It    results  from  the  tryptic 

*  Bernthsen,  Organic  Chemistry. 

t  Foster,  Chemical  Basis  of  the  Animal  Body. 

t  Novy,  Physiological  Chemistry. 


PLATE  v.— ORGANIC  CHEMISTRY. 


Fig.  3. 
Urea  Nitrate. 


Fig.  4. 
Hippuric  Acid. 


Fig.  5. 
Benzoic  Acid  (sublimed). 


Fig.  6. 
Tyrosin. 


ORGANIC  ACIDS  223 

digestion   of    the  hemipeptones  and  is  regarded,  as  are  other 
amino  acids,  as  antecedent  of  urea  (Plate  V,  Fig.  2). 

Cystin,  C6H12N2S2O4,  is  an  amino  acid  occasionally  found  in 
the  urine  in  diseases  where  the  sulphur  compounds  fail  to  be 
properly  oxidized.  It  occurs  under  these  circumstances  as  reg- 
ular colorless  hexagonal  plates  (Plate  X,  Fig.  6). 

By  the  oxidation  of  crystin  and  subsequent  spHtting  off  of 
CO2  taurine  is  produced. 

CH2NH2 

Taurine,  (Amino-ethyl-sulphonic  acid)  I  ,   results 

CH2(S020H) 
from  the  cleavage  of  protein,  also  from  the  decomposition  of 
taurocholic  acid  from  bile. 

Leucin,  (CH3)2.CH.CH2.CHNH2.COOH),  is  an  a  amino  iso- 
butyl  acetic  acid  and  occurs  usually  with  tyrosin  as  a  decompo- 
sition product  of  protein  (casein) .  It  is  occasionally  found  in  the 
urine  as  "leucin  spheres"  (represented  in  Plate  V,  Fig.  2). 

Tyrosin  is  a  complex  amino  acid  obtained  from  the  decom- 
position of  protein  substances,  particularly  old  cheese.  It  is  oc- 
casionally found  in  urinary  sediments  as  colorless  needle-shaped 
crystals  usually  grouped  as  tufts  or  "■  sheaves."     (Plate  V,  Fig.  6) . 

Dibasic  Amino  Acids. 

Of  this  class  of  compounds  two  may  be  mentioned:  amino- 
succinic,  aspartic  or  asparaginic  acid,  COOH-CH2-CH(NH2)- 
COOH,  may  be  obtained  from  animal  and  vegetable  proteins 
and  in  the  pancreatic  digestion  of  fibrin. 

Glutamic  Acid  is  an  amino-glutaric  (pyrotartaric)  acid,  and 
occurs  similarly  to  aspartic  acid,  except  that  it  is  not  formed  by 
pancreatic  digestion. 

Laboeatory  Exercise  LVI. 

Experiments  with  Organic  Acids  not  of  the  Call 2  n02  Series. 

Exp.  84.  To  a  dilute  solution  of  permanganate  of  potassium 
add  a  few  drops  of  sulphuric  acid  and  heat  nearly  to  boiling. 


224  ORGANIC  CHEMISTRY 

Note  if  any  change  takes  place.  Now  add  a  few  crystals  of  ox- 
alic acid  and  watch  carefully.     Explain  the  use  of  sulphuric  acid. 

Exp.  85.  In  separate  test-tubes,  insoluble  oxalates  may  be 
produced  by  adding  a  solution  of  ammonium  oxalate  to  a  solu- 
tion of  {a)  calcium  chlorid,  (&)  silver  nitrate,  (c)  zinc  sulphate, 
{d)  copper  sulphate,  (e)  lead  nitrate. 

Exp.  86.  Place  in  an  ignition-tube,  fitted  with  delivery-tube 
to  collect  evolved  gas  in  test-tube,  about  3  grams  of  dry  calcium 
oxalate.  Heat  strongly  and  test  gas  evolved  with  lighted  match 
or  splinter.  After  ignition-tube  has  become  cold  add  dilute 
H2SO4  and  pass  gas  evolved  into  lime  water. 

Exp.  87.  Dissolve  about  3  grams  of  dry  oxalic  acid  (100°  C.) 
in  a  test-tube  half  full  of  methyl  alcohol.  It  will  probably  be 
necessary  to  boil  the  mixture  before  solution  is  complete  and 
great  care  must  be  used  to  avoid  burning  of  the  alcohol.  The 
use  of  a  water-bath  is  recommended.  As  the  hot  mixture  cools, 
dimethyloxalate  will  crystalHze  out. 

Separate  sufficient  of  the  crystals  to  obtain  melting-point, 
which  should  be  about  54°  C. 

Exp.  88.  The  ester  prepared  in  above  experiment  may  be 
dissolved  in  alcohol  and  upon  addition  of  NH4OH  will  give  a 
precipitate  of  oxamid. 

Exp.  89.  Take  a  test-tube  half  full  of  calcium  chlorid  (10%), 
make  strongly  alkaline  with  NH4OH  and  pass  CO2  into  the 
mixture  for  several  minutes.  A  solution  of  calcium  carbonate 
will  result. 

Write  reaction,  CaCla  -h  2  CO2  +  4  NH4OH  =  ?.  Heat  the 
solution  of  calcium  carbonate  just  produced  till  a  precipitate  of 
CaCOs  is  produced. 

Write  reaction  with  one  molecule  of  water  on  left-hand  side 
of  equation. 

Exp.  90.  To  1/3  test-tube  of  cider  vinegar  add  a  few  cubic 
centimeters  of  basic  acetate  of  lead  solution;  a  bulky  precipitate 
of  lead  malate  separates  out. 


ORGANIC  ACIDS  225 

Exp.  91.  Dilute  a  few  drops  of  neutral  ferric  chlorid  solu- 
tion until  no  color  is  discernible,  then  to  10  c.c.  of  this  dilution 
add  4  to  5  drops  of  1/2%  solution  of  lactic  acid.  A  greenish- 
yellow  color  constitutes  the  test. 

In  practical  application  of  this  test,  it  needs  further  con- 
firmation by  boiling  the  unknown  solution  with  a  drop  or  two 
of  HCl  and  then  extracting  with  ether.  Evaporate  the  ether, 
take  up  the  residue  in  2  or  3  c.c.  of  water  and  repeat  the  test 
as  given  above.  If  the  yellow  color  persists,  it  is  due  to  lactic 
acid. 


CHAPTER  XXV. 
AMINS   OR   SUBSTITUTED   AMMONIAS. 

If  one  or  more  of  the  H  atoms  of  ammonia,  NH3,  be  replaced 
by  a  hydrocarbon  group,  the  resulting  compound  is  an  amin; 
thus  CH3-NH2  is  methylamin,  and  (CH3)2NH  is  dimethylamin. 
Trimethylamin,  (CH3)3N,  has  been  found  among  the  decom- 
position products  of  fresh  brain,  human  liver,  and  spleen.* 
It  is  poisonous  and  possesses  a  strong,  fishy  odor.  At  ordi- 
nary temperature  it  is  a  gas,  but,  like  ammonia,  is  freely  soluble 
in  H2O  and  forms  a  variety  of  salts. 

Diamins  are  derived  from   two  molecules  of   ammonia,  as 

/NH2 
ethylene  diamin,  C2II4 

^NH2 
To  this  class  of  compounds  belong  many  of  the  "ptomains, " 
produced  by  the  putrefaction  of  organic  matter,  as  putrescin, 
(butylene  diamin),  CH2NH2-(CH2)2-CH2NH2,  and  cadaverin, 
(pen ta-methylene  diamin) ,  CH2NH2-(CIl2)3-CIl2NH2.  A  large 
number  of  the  ptomains  are  aromatic  compounds  and  as  such 
will  be  referred  to  later. 

Amids. 

If  the  hydrogen  of  NH3  be  replaced  by  an  oxygenated  or 
acid  radical,  an  amid  results;  thus  NH2(C2H30)  is  acetamid, 
or  this  compound  may  be  regarded  as  acetic  acid,  CH3-COOH, 
in  which  the  OH  has  been  replaced  by  NH2. 

Formamid,  CHO.NH2,  is  a  liquid  miscible  with  both  alcohol 
and  water.     It  boils  with  partial  decomposition  at  about  200°  C. 

*  Vaughn  and  Novy,  Cellular  Toxins. 
226 


AMINS  OR  SUBSTITUTED  AMMONIAS  227 

Upon  heating  quickly,  it  splits  into  CO  and  NH3.     (Bernthsen.) 
Phenyl-formamid,  CHO.NHCeHs,  known  as  formanilid,  occurs 
as  yellow  crystals  soluble  in  water  and  in  alcohol. 

Hydrazines. 

From  diamid,  NH2-NH2,  or  hydrazine,  may  be  derived  such 
substitution  products  as  methyl-hydrazine,  CH3-NH-NH2 ;  ethyl- 
hydrazine,  C2H5-NH-NH2 ;  andphenyl-hydrazine,  C6H5NH-NH2. 

This  latter  compound  forms,  with  the  monosaccharids  and 
with  many  of  the  disaccharids,  yellow  crystalline  compounds, 
known  as  osazones,  which  are  precipitated  in  characteristic 
crystalhne  forms,  recognizable  upon  microscopical  examination 
and  by  their  melting-points  (see  under  Carbohydrates,  page  260). 


CHAPTER  XXVI. 
CYANOGEN   COMPOUNDS. 

Cyanogen,  C2N2,  is  an  intensely  poisonous  gas,  colorless, 
heavy  (specific  gravity  1.81),  and  inflammable.  It  is  very 
easily  soluble  in  water  or  alcohol,  forming  unstable  solutions, 
which,  upon  decomposition,  give  rise  to  various  nitrogen  com- 
pounds, among  them  ammonia,  hydrocyanic  acid,  and  urea. 

Hydrocyanic  Acid,  HCN,  may  be  produced  by  the  fer- 
mentation of  the  glucoside  amygdalin  from  bitter  almonds; 
also  from  the  kernel  of  peach-stones,  cherry-laurel  leaves,  etc. 
HCN  may  be  formed  by  direct  synthesis  of  C2H2  (acetylene) 
and  nitrogen.  The  synthesis  is  induced  by  passing  electric 
sparks  through  the  mixed  gases.  It  is  conveniently  prepared 
in  the  laboratory  by  distilling  a  mixture  of  dilute  sulphuric 
acid  with  potassium  ferrocyanide,  K4Fe(CN)6  +  5  H2SO4  = 
6  HCN  -\-  FeS04  -\-  4  KHSO4.  Hydrocyanic  acid  is  a  colorless, 
poisonous  liquid,  boiling  at  26.5°  C,  with  a  characteristic  odor 
often  designated  as  a  peach-stone  odor.  It  is  soluble  in  H2O, 
and  a  2%  aqueous  solution  constitutes  the  acidum  hydrocyani- 
cum  dilutum  of  the  pharmacopoeia,  also  known  as  prussic  acid. 

Potassium  Cyanide  (KCN  or  KCy)  occurs  in  trade  as  a  white 
solid,  sometimes  granular,  more  often  as  a  powder.  It  is  in- 
tensely poisonous  owing  to  the  dissociation  of  the  salt  and  activ- 
ity of  the  free  cyanogen. 

KCN  is  decomposed  by  carbonic  acid  of  the  air  with  liber- 
ation of  HCN.  The  aqueous  solution  of  KCN  hydrolyzes  in 
two  distinct  ways:  the  most  easily  apparent  at  ordinary  tem- 
perature is  with  the  formation  of  HCN  and  KOH  giving  the 
solution  an  alkaHne  reaction: 

KCN  +  H2O  =  HCN  +  KOH. 

228 


CYANOGEN   COMPOUNDS  229 

Upon  boiling  a  solution,  the  second  hydrolysis  may  be  dem- 
onstrated whereby  NH3  and  potassium  formate  are  produced : 

KCN  +  2  H2O  =  HCOOK  +  NH3  (Exp.  96,  page  230). 

The  organic  cyanids  are  known  as  nitrils  or  isonitrils,  accord- 
ing as  the  hydrocarbon  radical  is  attached  directly  to  the  C  or 
to  the  N  of  the  cyanogen  group.  That  is,  methyl  cyanid  would 
be  represented  by  CH3-CN,  while  the  isocyanid  would  be 
CH3-NC  (methyl  carbamin);  the  nitrogen  atom  being  in  the 
first  place  trivalent,  in  the  second  quinquivalent. 

Of  these  two  classes  of  compounds,  the  isocyanids  are  of 
much  greater  interest  to  the  student  of  dental  medicine  owing 
to  their  relation  to  the  isocyanates  and  to  urea. 

Phenyl-isocyanid,  CsHeNC,  also  known  as  isobenzonitril, 
is  produced  by  warming  aniline  (C6H5NH2)  with  alcohoKc 
potash  and  chloroform,  the  intensely  disagreeable  odor  of 
which  is  utilized  as  a  test  for  chloroform  or  chloral  hydrate 
(page  167);  or,  with  chloroform  and  potassium  hydrate,  the 
production  of  isocyanid  may  become  a  test  for  aniline,  acetaniHd 
(antif ebrin) ,  etc. 

Isocyanic  Acid,  0  =  C  =  N-H  (carbimid),  is  supposed  to  be 
the  acid  of  ordinary  potassium  and  ammonium  cyanates. 

Fulminic  acid  (C  =  N-O-H),  isomeric  with  cyanic  acid 
N  =  C-O-H  and  isocyanic  acid  (0  =  C  =  N-H),  is  important 
only  because  of  its  relation  to  the  fulminates,  which  are  explosive 
compounds  of  the  acid,  with  some  of  the  heavy  metals,  such  as 
Ag  and  Hg. 

Thiocyanic  Acid  or  Sulphocyanic  Acid.  —  In  this  acid  and 
its  salts,  the  atom  of  S  replaces  the  oxygen  of  the  cyanate  in 
the  empirical  symbol  (HCNS) ;  but,  graphically,  the  S  is  attached 
to  the  basic  element  (metal  or  H)  rather  than  to  C:  thus, 
K-S-C  =  N,  that  is,  the  sulphocyanate  is  not  an  isocompound. 
For  occurrence  and  relations  of  HCNS  in  the  human  body,  see 
chapter  on  Saliva. 


230  ORGANIC  CHEMISTRY 

Laboeatory  Exercise  LVII. 
Experiments  with  Cyanogen  Compounds. 

Exp.  92.  In  a  test-tube  dissolve  1/2  gram  or  less  of  potas- 
sium ferrocyanid  in  about  4  c.c.  of  H2O.  Add  a  little  H2SO4  and 
boil,  conducting  the  gas  evolved  into  another  test-tube  by  means 
of  a  bent  glass  tube.  Note  the  odor  of  this  dilute  solution. 
(Do  not  smell  of  the  contents  of  generating-tube,  as  the  strong 
acid  is  intensely  poisonous.) 

2  K4FeCy6  +  6  H2SO4  =  KaFeCFeCye)  +  6  KHSO4  +  6  HCy. 

Exp.  93.  To  one  half  of  the  dilute  hydrocyanic  acid  prepared 
in  the  previous  experiment  add  a  drop  or  two  of  AgNOs  solu- 
tion with  a  little  HNO3.  After  the  precipitate  has  settled, 
decant  the  fluid,  then  add  an  excess  of  ammonia-water. 

Exp.  94.  To  the  other  half  of  the  HCy  from  Exp.  92  add  a 
Httle  solution  of  ferrous  sulphate;  also  a  few  drops  of  ferric 
chlorid  solution;  then  a  little  KOH  solution;  mix  thoroughly 
and  acidify  with  HCl.  A  blue  precipitate,  Fe4(FeCy6)3,  is  a  test 
for  HCy  or  any  soluble  cyanid. 

Exp.  95.  To  a  few  drops  of  KCN  solution  add  a  httle 
yellow  ammonium  sulphid,  (NH4)2S,  and  evaporate  to  dryness. 
Dissolve  in  water;  acidify  with  HCl  and  add  Fe2Cl6  solu- 
tion. 

Exp.  96.  In  a  small  flask  boil  a  solution  of  KCN.  While 
boiling,  test  the  vapors  for  ammonia  gas.  Solution  of  potassium 
formate  remains  in  the  flask. 

Complete  reaction,  KCN  +  2  H2O  =  ?. 

Exp.  97.  To  a  httle  dilute  (2%)  solution  of  K4FeCy6  add 
a  httle  bromin  water  and  boil.  Prove  the  formation  of  KsFeCye 
by  use  of  FeCls- 

From  this  experiment  what  is  the  relative  valence  of  iron  in 
the  two  compounds?    Why? 


CYANOGEN  COMPOUNDS  231 

Exp.  98.  To  a  fresh  solution  of  KsFeCye  add  a  little  10% 
KOH  solution  and  some  PbO,  shake  and  filter.  To  the  clear 
filtrate  add  FeCls. 

Give  reason  for  the  statement  that  the  PbO  has  acted  as  a 
reducing  agent. 


CHAPTER  XXVII. 
UfeEA. 

This  substance  forms  about  50%  of  the  total  solids  and 
about  85%  of  the  nitrogenous  matter  contained  in  the  urine. 
When  we  consider  that  only  5%  of  the  nitrogenous  waste  passes 
off  in  the  feces  and  95%  in  the  urine,  the  importance  of  urea  as 
an  index  of  the  nitrogen  excreted  and  of  protein  metabolism 
becomes  apparent. 

Urea  was  the  first  organic  substance  synthesized  from  in- 
organic compounds.  This  was  accompHshed  by  producing  a  mo- 
lecular rearrangement  of  ammonium  isocyanate.  The  reaction 
is  conveniently  brought  about  by  the  double  decomposition  of 
potassium  cyanate  and  ammonium  sulphate  and  subsequent 
evaporation  of  the  solution  to  dryness : 

2  CNOK  +  (NHOaSO  =  OCN.NH4  +  K2SO4. 
Then  O  =  C  =  N  -  NH4  (ammonium  isocyanate)  +  heat  = 

/NH2 
0  =  C  (urea). 

/OH 

Urea  is  the  amid  of  carbonic  acid,  0  =  C  ,  and  from  this 

^OH 
type  may  be  explained  the  rapid  transformation  of  urea  into 

/NH2 
ammonium    carbonate    in    stale  urine.     O  =  C  with  one 

^NH2 
/  ONH4 
molecule  of  H2O  becomes  O  =  C  or   ammonium   carba- 

^NH2 
mate,  and  this,  by  addition  of  a  second  molecule  of  water,  be- 

232 


UREA  233 

comes  O  =  C  or  ammonium  carbonate,  (NH4)2C03.   The 

^0NH4 
last  part   of   the   reaction   takes   place   whenever    commercial 
"ammonium    carbonate"     [really    a    mixture     of    carbamate 
(NH4-NH2-CO2)  and  acid  carbonate  (NH4HCO3)]  is  dissolved 
in  water. 

Urea  crystallizes  in  long  needle-shaped  crystals  of  the  rhom- 
bic system.  It  is  insoluble  in  water,  somewhat  soluble  in 
alcohol,  and  nearly  insoluble  in  ether.  It  fuses  at  132°,  and  at 
a  somewhat  higher  temperature  it  gives  off  ammonia  and  am- 
monium carbonate,  and  at  160°  leaves  a  residue  of  ammelid, 
cyanuric  acid,  and  biuret.  Urea  is  decomposed  by  solutions  of 
the  alkahne  hypochlorites  or  hypobromites  being  broken  up  into 
N,  CO2,  and  H2O,  as  follows: 

CO(NH2)2  +  3  NaOBr  =  CO2  +  N2  -F  2  H2O  +  3  NaBr. 

Cyanuric  Acid,   (N3C3O3H3),  is  a  polymer  of  cyanic  acid 
(NCOH),  which  is,  at  first,  formed  in  the  above  decomposition. 
/CO-NH2 

Biuret,  H  — N  ,  may  be  obtained  by  heating  urea. 

^CO-NHs 
When  pure,  it  occurs  as  white,  needle-shaped  crystals.     With 
NaOH  and  1%  CUSO4  it  gives  the  characteristic  violet  and  rose- 
red  shades  obtained  in  the  biuret  reaction  (Piotrowski's  proteid 
test).     Exp.  157,  page  277. 

Urea  Nitrate  may  be  precipitated  from  fairly  concentrated 
urine  by  addition  of  HNO3.  It  separates  in  hexagonal  crystals 
or  plates,  easily  recognizable  imder  the  microscope  (Plate  V, 
Fig.  3,  opposite  page  222). 

Urea  Oxalate.  —  Upon  addition  of  a  solution  of  oxahc  acid 
to  concentrated  urine,  crystals  of  oxalate  of  urea  are  precipi- 
tated. They  are  rather  more  easily  obtained  in  characteristic 
forms  (Plate  II,  Fig.  5,  opposite  page  162)  than  are  the  crystals 
of  nitrate,  and,  in  consequence,  treatment  with  oxahc  acid  con- 
stitutes a  better  method  for  the  quahtative  detection  of  urea  in. 


234  ORGANIC  CHEMISTRY 

the  body  fluids  than  the  nitric  acid  test  formerly  used.  These 
crystals  polarize  light,  and  the  use  of  the  micropolariscope  faciH- 
tates  their  detection. 

Substituted  Ureas.  —  The  hydrogen  of  the  amino  group 
may  be  replaced  by  alcohol  radicals  forming  what  are  known 

/HN2 

as   alkylated  ureas;    thus,   O  =  C  is   methyl   urea, 

^NHCHs 
/NH2 
0  =  C  ,  ethyl  urea,  and  one,  two,  three,  or  all  four  of 

^NHCaHs 
the  H  atoms  may  be  so  replaced. 

When,  in  place  of  an  alcohol  radical,  the  acid  radical  is  in- 
troduced, a  class  of  compounds  known  as  "ureids"  results;  thus, 
/NH2 

NHCCgHsO) (acetyl  urea). 

COOH 
In  case  of  a  dibasic  acid,  such  as  oxalic,   i  ,  entering 

COOH 

into  the  reaction,  one  or  both  (OH)  groups  may  be  spHt  off,  form- 

/NH2 
ing  in  the  first  instance  a  ureid  acid,  as  0  =  C  ' 

^NH.CO,  COOH 
oxaluric  acid, 

COOH  /NH2  /NH2 

I  +0  =  C  =0  =  C  +H2O 

COOH  ^NH2  ^NH-CO 

I 

COOH 
/NH-C  =  0 
or,  in  the  second  case,  a  ureid,  as  0  =  C  I  parabanic 

^NH-C  =  0 
acid. 

If  the  residue  of  two  molecules  of  urea  enter  into  the  com- 
position of  the  new  molecule,  the  compound  is  a  diureid.  Of 
this  class  one  of  the  most  important  is: 


UREA  '  235 

Uric  Acid,  trioxypurin,  C5H4N4O3.     Its  relation  to  urea  may 

NH-CO 
I        I 
be  shown   by  the   graphic   formula  0  =  C      C-NH^ 

I        II  C  =  O 

NH-C-NH  ^ 

Uric  acid  is  also  referable  to  a  purely  h3rpothetical  base,  "purin, " 
by  the  use  of  which  the  relationship  of  xanthin,  hypoxanthin, 
and  other  ''purin"  or  nuclein  bases  is  easily  demonstrated. 

These  bases  are  of  great  physiological  interest,  in  that  they 
form  an  unquestioned  link  between  the  decomposition  products 
of  the  proteins,  nuclein,  etc.,  on  the  one  hand,  and  uric  acid 
and  the  urates  on  the  other. 

Purin  is  represented  by  the  formula  C5H4N4,  or  graphically 
N  =  C-H 

I  i 

as  H-C      C-N-H       .     If  we  now  break  all  double  bonds  ex- 

II  II       )C-H 
N-C-N^ 

cept  those  linking  two  carbon  atoms  (4  and  5),  we  obtain  a 

I  -  N-C« 


graphic  nucleus,  2  =  C  C^-N  —  7  ,  by  numbering  the  atoms 

I     II        )C  =  8 
3-N-C4-N-9 
of  which  we  may  easily  designate  any  structural  formula  of  the 
group;    thus,   2-6-8,  trioxypurin,  is  uric  acid  as  above,  while 

H-N-C  =  O 
I     I 
xanthin  is    2-6,   dioxypurin,   O  =  C  C-N-H       ,    and    1-3-7, 

I     II        )  C-H 
H-N-C-N^ 
CH3-N-C  =  O 
I     I 
trimethyl-xanthin,    O  =  C  C  —  N  —  CH3,  is  caffein   and    thein, 

I     II  ^C-H 

CH3-N-C-N^ 
alkaloids  from  coffee  and  tea. 


236  ORGANIC  CHEMISTRY 

Traces  of  xanthin  (2.6  dioxypurin) ,  hypoxanthin  (6  oxy- 
purin),  guanin  (2  imino,  6  oxypurin),  adenin  (6  amino  purin), 
and  heteroxanthin  (7  methyl  xanthin)  have  been  found  in  urine, 
and,  in  cases  of  leukaemia,  many  of  them  in  increased  amounts, 
notably  xanthin,  hypoxanthin,  and  adenin  (Witthaus). 

Uric  acid  occurs  in  the  urine ;  there  are  traces  of  it  in  the  blood ; 
and  it  is  occasionally  found,  in  the  form  of  urates,  in  saliva.  It 
is  a  dibasic  crystalline  acid,  colorless  when  pure;  but,  in  uri- 
nary sediment,  it  occurs  generally  as  crystals,  yellow  to  red, 
"whetstone "-shaped,  and  in  various  other  forms  (Plate  X,  Figs. 
I  and  2).  The  "brickdust"  deposit  occasionally  found  in  urine 
consists  of  uric  acid.  It  is  insoluble  in  alcohol  and  nearly 
insoluble  in  water;  but  its  solubility  in  water  is  increased  by  the 
presence  of  urea. 

Upon  heating  uric  acid,  urea  and  cyanuric  acid  may  be  ob- 
tained; NH3  and  CO2  are  given  off.  We  are  not  to  infer 
from  this  decomposition  that  the  uric  acid  is  an  antecedent  of 
urea  in  the  animal  body;  for  such  is  not  the  case,  except  possibly 
to  a  limited  extent. 

Uric  acid  produces,  upon  oxidation,  a  variety  of  compounds, 
according  to  the  temperature  and  the  oxidizing  agent  employed. 

CI,  hot,  yields  cyanuric  acid,  €3113(011)3.     CI  or  Br,  cold, 

,       /NHCO\       ^ 

forms  oxalic  acid,  alloxan,  (CO^  ^CO),  parabamc  acid, 

^NHCO^ 

/       /NH-CO\ 

ICO  I     I,  and  ammonium  cyanate.     HNO3  in  the  cold, 

\       ""NH-CO/ 

forms  alloxan,  alloxantin,  and  urea  (Witthaus). 

Uric  acid  may  be  detected  by  the  murexid  test.  See  Exp.  104, 
page  239. 

While  uric  acid  is  practically  insoluble  in  H2O  and  the  acid 
urates  only  sparingly  soluble,  the  uric  acid  in  the  system  is 

Note.  —  Murexid  is  a  definite  chemical  compound   (CsHsNjOe)  and  may  be 
produced  from  alloxantin,  an  oxidation  product  noted  above. 


UREA  237 

apparently  held  in  solution  as  an  acid  urate  (NaHU)  by  the 
presence  of  the  sodium  phosphates,  NaH2P04  and  Na2HP04, 
possibly  also  aided  by  the  presence  of  some  unknown  organic 
combination. 

NaHU  +  NaH2P04  forms,  at  38°  C,  a  solution  with  an  acid 
reaction;  if,  however,  the  mixture  is  cooled  to  room  tempera- 
ture, the  reaction  becomes  alkahne  from  Na2HP04,  and  uric 
acid  is  precipitated  (Bunge) : 

NaHU  +  NaH2P04  =  Na2HP04  +  H2U. 

Na2HP04  is  a  normal  constituent  of  the  blood,  and  a  tendency 
to  precipitate  uric  acid  may  be  met  by  the  following  reac- 
tion :  Na2HP04  +  H2U  =  NaH2P04  +  NaHU.  Because  the  acid 
urate  of  lithium  is  much  more  soluble  in  water  than  any  of  the 
other  monometallic  urates,  lithium  salts  have  long  been  used  as 
uric  acid  solvents.  But  the  fact  that  lithium  solutions  will 
precipitate  from  solutions  of  Na2HP04  crystals  of  Li2HP04,  has 
been  made  the  basis  for  a  claim  that  such  use  of  lithium  salts  is 
without  effect  other  than  to  decompose  and  render  insoluble 
the  alkaline  phosphate,  which  has  been  acknowledged  a  valu- 
able factor  in  keeping  uric  acid  in  solution.  While  the  disodic 
phosphate  is  regarded  by  many  as  superior  to  lithium  salts  as 
a  uric  acid  solvent,  the  fact  of  comparative  insolubility  of 
Li2HP04  can  hardly  be  regarded  as  conclusive  evidence  that 
lithium  compounds  are  not  effective. 

The  following  in  regard  to  our  need  for  "  sarsaparilla "  in 
the  spring  is  given  by  Dr.  E.  C.  Hill,  of  the  University  of  Den- 
ver, in  his  text-book  of  chemistry,  page  370:  "Reduced  alka- 
linity of  the  blood,  as  in  winter  from  eating  meats  freely,  throws 
uric  acid  out  of  solution  to  collect  in  the  more  acid  tissues  (spleen, 
liver,  and  joints).  With  the  vernal  tide  of  alkalinity  (due  to 
freer  sweating,  with  excretion  of  fatty  acids)  these  deposits  are 
swept  out  in  the  blood-current,  irritating  the  nerves  and  giving 
rise  to  'that  tired  feeling.'" 


238  ORGANIC  CHEMISTRY 

Laboratory  Exercise  LVIII. 
Urea  and  Uric  Acid. 

Exp.  99,  Make  separate  solutions  of  10  grams  of  potassium 
cyanate  *  and  8.25  grams  of  ammonium  sulphate.  Mix  and 
evaporate  on  a  water-bath  in  a  shallow  dish.  Separate  the 
potassium  sulphate  as  the  evaporation  proceeds;  finally,  evapo- 
rate to  dryness  and  extract  with  absolute  alcohol.  Evaporate 
alcohol  and  reserve  the  urea  for  subsequent  experiments.  (See 
Urea,  page  232.) 

Exp.  100.  Heat  a  few  crystals  of  urea  in  a  test-tube  until  they 
fuse  and  no  more  gas  is  given  off;  cool,  and  dissolve  the  fused 
mass  in  water;  add  one  or  two  c.c.  of  strong  NaOH  solution, 
then  not  more  than  one  or  two  drops  of  a  1%  CUSO4  solution. 
Note  the  pink  to  violet  color  produced.  This  constitutes  the 
biuret  reaction  used  in  physiological  chemistry  as  a  test  for 
albumoses  and  peptones.     Biuret  is  formed  from  urea  as  follows: 


NH2      0  =  C 


/NH2 


^NH2 

Exp.  loi.  Produce  crystals  of  urea  nitrate  and  oxalate 
(page  233)  and  examine  under  the  microscope.  Repeat  with  urea 
obtained  from  urine. 

This  experiment  may  be  performed  by  concentrating  to 
about  1/5  its  bulk  a  little  urine  and  using  the  concentrated  solu- 
tion as  a  solution  of  urea. 

Exp.  102.  Treat  5  c.c.  of  urea  solution  (urine  may  be  used) 
with  a  little  sodium  h3rpochlorite  or  hypobromite;  note  results 
and  study  reaction  given  on  page  233. 

*  For  method  of  making  potassium  cyanate,  see  Preparation  of  Reagents  and 
Organic  Compounds,  in  the  Appendix. 


UREA  239 

Exp.  103 .  Heat  one- third  of  a  test-tube  of  urine  with  barium 
hydroxid  (bary ta- water) ;  test  vapor  with  red  Htmus  for  NH3. 

Exp.  104.  Murexid  test  for  uric  acid :  Place  a  very  small 
quantity  of  uric  acid  on  a  porcelain  crucible  cover,  or  in  a  small 
evaporating-dish.  Add  two  or  three  drops  of  strong  nitric  acid 
and  evaporate  to  dryness  over  a  water-bath.  A  yellowish-red 
residue  remains,  which  changes  to  a  purplish  red  upon  addition 
of  a  drop  of  strong  NH4OH,  and  purple-violet  upon  further 
addition  of  a  drop  of  KOH  solution,  the  color  disappearing 
upon  standing  or  upon  the  application  of  heat.  (Difference 
from  xanthin,  which  also  gives  a  deeper  red  color.) 

Exp.  105.     Repeat  No.  104,  using  caffein  in  place  of  uric  acid. 

Exp.  106.  Heat  a  little  sodium  acid  urate  in  a  dilute  solution 
of  NaH2P04.  Allow  to  cool,  and  examine  any  deposit  for  uric 
acid  crystals.  Test ,  reaction  of  solution  both  hot  and  cold 
(page  237). 

Exp.  107.  Mix,  and  allow  to  stand  for  some  time  at  reduced 
temperature,  30  c.c.  of  urine  (a  2%  urea  solution),  2  or  3  c.c.  of 
strong  Na2C03  solution,  and  5  c.c.  of  saturated  NH4CI  solution. 

A  precipitate  consists  of  ammonium  urate. 

Examine  under  the  microscope  and  make  murexid  test. 


CHAPTER  XXVIII. 
CLOSED-CHAIN  HYDROCARBONS. 

In  illustrating  the  simpler  relationship  of  organic  compounds 
we  have,  as  far  as  possible,  carefully  avoided  reference  to  the 
closed-chain  or  aromatic  compounds,  as  the  characteristic  group- 
ings are  more  easily  seen  by  the  use  of  simple  formulae.  The 
distinguishing  feature  of  the  aromatic  (also  called  cyclic)  com- 
pounds is  a  nucleus  consisting  of  a  closed  chain  of  atoms;  this 
chain  may  contain  three,  four,  five,  six,  or  seven  members,  but 
the  six-carbon  ring  is  by  far  the  most  important,  and  the  only 
one  which  we  are  to  consider. 

The  hydrocarbons  of  the  aromatic  series  have,  for  a  general 
formula,  CnH2n-6,  the  simplest  being  benzene  or  benzol,  CeHe; 
and  we  may  consider  that  the  aromatic  compounds  are  derived 
from  this.  The  structure  of  the  benzene  molecule  is  repre- 
sented by  "Kekule's"  benzene  ring.  Note  that 
there  are  three  double  bonds,  which  of  course  , 

permit  of  addition  products,  as  C6H6CI2,  ben-  q 

zene  di-chlorid,  etc.     The  substitution  products     jj_r;        C-H 
are,  however,  of  far  greater  importance.  I  n 

Benzene,  CeHe  (benzol),  is  a  colorless  liquid  H-C  C-H 
from  the  "light-oil"  obtained  by  distillation  of  ^C^ 

coal-tar.     It  boils  at  80°,  has  a  gravity  of  0.899,  ' 

is  soluble  in  ether,  alcohol,  and  chloroform,  but 
insoluble  in  H2O.  It  may  be  made  pure  by  distilling  an  inti- 
mate mixture  of  benzoic  acid  and  quickHme,  and  at  a  temper- 
ature of  about  5°  C.  may  be  obtained  as  a  crystalline  solid, 
CeHsCOGH  -I-  CaO  =  CaCOs  +  CeHg.  (See  Exp.  108,  page 
250.) 

240 


CLOSED-CHAIN  HYDROCARBONS  241 

Toluene,  CyHs  (toluol).  — The  next  higher  homologue  of  the 
series  will  be  CyHg;  this  is  methyl  benzene,  (C6H5CH3),  or 
toluene. 

The  hydrocarbons  of  this  series  may  be  prepared  in  a  manner 
similar  to  that  used  in  the  preparation  of  the  hydrocarbons  of 
the  parafiin  series. 

Toluene  may  be  made  by  the  action  of  metaUic  sodium  upon 
a  mixture  of  brombenzene  and  methyl  iodid. 

CeHsBr  +  CH3I  +  Na2  =  C6H5CH3  +  NaBr  +  NaT 

Toluene  is  a  colorless  liquid  boiling  at  110°  C,  and  yielding 
upon  oxidation  a  benzene  derivative;  i.e.,  the  CH3,  or  so-called 
side  chain,  is  the  part  of  the  compound  changed  by  oxidizing 
agents  rather  than  the  benzene  ring, 

C6H5CH3  +  30  =  C6H5CO2H  +  H2O. 

Xylene,  CgHio  (xylol)  or  dimethylbenzene,  the  next  hydro- 
carbon of  this  series,  exists  in  coal  tar  as  a  mixture  of  three 
isomeric  compounds  which  may  be  graphically  represented  as 
follows : 

CH3  CH3  CH3 


CH3         {     >,  J 

,      .  ,      ,r-cT  and 

CH3 


These  three  possible  positions  of  the  second  substitution  are 
known  as  ortho-,  meta-,  and  para- ;  thus,  the  first  representation 
at  the  left  will  be  ortho-xylene,  or  ortho-dimethylbenzene.  The 
other  two  will  be  meta-xylene  and  para-xylene  respectively. 

A  trisubstituted  benzene  may  be  "adjacent,"  if  the  sub- 
stituted element  or  group  is  attached  to  the  carbon  atoms  1-2-3 
or  " uns3anmetrical "  (1-2-4)  or  "symmetrical"  (1-3-5)- 

A  fourth  isomer  of  dimethylbenzene  would  be  an  ethyl 
benzene,  C6H5C2H5.  This,  upon  oxidation,  yields  benzoic  acid, 
a  benzene  derivative  in  a  manner  similar  to  toluene. 


242  ORGANIC  CHEMISTRY 

Mesitylene,  C9H12,  is  a  trimethylbenzene.  Only  two  isomers 
are  possible.  It  can  be  prepared  by  dehydrating  acetone  by 
the  use  of  sulphuric  acid : 


3  C3H6O  -  3  H2O  =  C9H: 


12- 


Dertvatr^es  of  the  Hydrocarbons  of  the  Aromatic  Series. 

The  derivatives  of  the  closed-chain  hydrocarbons  are  very 
numerous,  and  many  of  them  have  very  complex  formulae.  We 
shall  confine  our  study  to  a  few  of  the  most  simple  and  at  the 
same  time  most  common. 

The  halogen  derivatives  are  numerous  and  easily  made,  but 
are  not  of  particular  importance  from  a  dental  standpoint. 
The  hydroxyl  derivatives,  on  the  other  hand,  are  of  great  import- 
ance.    The  first  is  phenol. 

Phenol,  carbolic  acid,  or  oxybenzene,  CeHsOH,  obtained 
from  the  distillation  of  coal-tar,  and  used  as  an  antiseptic  and 
disinfectant.  For  properties  and  test,  see  page  174.  Phenol 
acts  like  an  acid,  in  that  it  forms  salts  with  the  metallic  bases, 
CeHsOK,  potassium  phenolate,  but  it  does  not  have  an  acid 
reaction  on  htmus  paper  or  other  indicators,  i.e.,  it  does  not 
have  free  hydrogen  ions  when  in  solution,  but  belongs  to  the 
alcohols  rather  than  the  acids. 

The  three  di-hydroxybenzenes  are  all  of  interest  and  are 
graphically  represented  as  follows: 

OH  OH 

/\    /-YLT    ortho-dibydroxy  /\  we/a-dihydroxy 

I  I  yJtX        benzene  or  i  i  benzene  or 

\/ 
and 

OH 


pyrocatechol  |         'OTT        resorcinol 


I         I  ^am-dihydroxy 

I          1  benzene  or 

V     /  hydroquinol 

OH 


CLOSED-CHAIN  HYDROCARBONS  243 

The  ortho  compound  is  p5rrocatechol.  Its  ethereal  sulphate 
(add  sulphate)  is  given  by  Hoppe-Seyler  as  a  constituent  of  nor- 
mal urine,  and  its  monomethyl  ether,  guaiacol,  C6H4OH-O-CH3, 
is  obtained  from  beech-wood  creosote,  of  which  it  constitutes 
the  greater  part  (60  to  90  per  cent  U.  S.  D.).  Guaiacol  and 
various  compounds  produced  from  it  have  been  widely  recom- 
mended for  tubercular  diseases. 

Pyrocatechol  has  been  found  to  be  the  most  practical  reagent 
for  the  detection  of  oxydizing  enzymes*  in  the  saliva. 

Resorcinol  is  a  white  crystalHne  sohd,  becoming  more  or  less 
colored  upon  exposure  to  the  light.  It  melts  at  118°  C,  and, 
in  solution,  gives  a  purple  color  with  ferric  chlorid.  Heated 
with  sodium  nitrate,  it  produces  a  substance  known  as  ''Lacmoid" 
which  is  used  to  a  considerable  extent  as  an  indicator. 

The  hydroquinol  or  hydrochinon,  is  a  white  powder  melt- 
ing at  169°  C,  and  is  largely  used  as  a  photographic  developer. 

Trihydroxybenzene,  or  pyrogalol,  C6H3(OH)3  (1-2-3),  i^3,y 
be  made  by  heating  gallic  acid,  and  because  of  this  fact  is  usu- 
ally called  pyrogalKc  acid.  It  is  a  white  silky  crystal  which, 
like  hydroquinol,  is  used  as  a  photographic  developer.  Dis- 
solved in  a  solution  of  caustic  potash  it  absorbs  oxygen  to  a 
marked  degree,  and  may  be  used  as  a  reagent  for  the  quantita- 
tive determination  of  oxygen  in  gas  analysis. 

Phloroglucinol  is  another  trihydroxybenzene,  isomeric  with 
pyrogalol  but  with  the  hydroxyl  groups  occupying  positions 
1-3-5  in  the  ring.     The  formula  is  C6H3(OH)3  (1-3-5). 

It  crystalHzes  in  rhombic  prisms,  soluble  in  water,  alcohol 
and  ether.  This  is  used  in  physiological  chemistry  as  a  reagent 
with  vanillin  as  a  test  for  free  hydrochloric  acid. 

Thymol  (3methyl-6  isopropyl-phenol),  C6H30H(j)  CHsfj,  CsHtj^^, 

is  a  solid  of  the  nature  of  camphor,  melting  at  44°  C,  and  is 

obtained  from  various   volatile   oils,   particularly  from  the  oil 

obtained  from  Thymus  Vulgaris.     It  is  very  sparingly  soluble  in 

*  Journal  of  the  Allied  Societies,  Vol.  4,  page  346.     Dec,  1909. 


244  ORGANIC  CHEMISTRY 

water.  The  addition  of  a  little  alcohol  increases  the  solubility. 
It  is  largely  used  in  the  preparation  of  antiseptic  dental  prepa- 
rations, mouth  washes,  etc. 

Phenol-sulphonic  Acid.  —  When  phenol  is  treated  with 
several  times  its  volume  of  cold,  strong  H2SO4,  phenol  sulphonic 

OH  OH 

acid,  r      1HSO3  or     |      1  results.     If  the  mixture  is  heated  for 

\/  \y 

HSO3 

some  time  over  a  water-bath,  the  disulphonic  acid  results.  This 
acid,  warmed  with  a  nitrate  and  the  mixture  treated  with  excess 
of  ammonia,  yields  ammonium  picrate,  and  constitutes  a  delicate 
test  for  nitrates  present  in  drinking-water. 

Phenol-sulphonic  acid  has  been  used  in  dentistry  as  a 
therapeutic  agent  (as  antiseptic  and  otherwise).  Such  use  is 
discussed  in  detail  by  Herman  Prinz,  M.D.,  D.D.S.,  in  the 
Dental  Cosmos  for  April,  191 2,  with  the  conclusion  that  the 
ortho  compound  is  several  times  more  active  than  either  the 
meta  or  para  compounds:  that  a  i  per  cent  solution  is  about 
equal  in  antiseptic  strength  to  a  i  per  cent  phenol  solution,  but 
in  this  strength  it  decalcifies  the  tooth  structure,  discolors  the 
teeth,  and  should  not  be  used  in  the  mouth  on  account  of  its 
pronounced  acid  character. 

Sulphonic  Acids  as  a  class  may  be  obtained  by  the  oxidation 
of  an  organic  sulphydrate  (mercaptan).  This  oxidation  may 
be  produced  by  the  action  of  HNO3  or  KMn04,  and  may  be 
written  as  follows: 

C2H5SH  +  30  =  C2H5.SO2.HO. 

Compounds  of  this  class  are  not  confined  to  the  hydro- 
carbons of  the  aromatic  series  as  the  above  typical  reaction 
shows. 

Aromatic  sulphonic  acids  may  be  made  by  a  similar  process : 

C6H5SH  -f  3  O  =  C6H5SO2HO, 


■  CLOSED-CHAIN  HYDROCARBONS  245 

and    also    by    the    action    of    sulphuric    acid    or    the    hydro- 
carbons. 

Sulphons   are  oxidation  products  of  organic  sulphids:    as, 

C2H5^    ^O 

or  example,  ethyl  sulphone  S 

Mercaptan,  an  organic  sulphydrate.  Representatives  of  this 
class  of  compounds  are  found  as  derivatives  of  both  the  open 
and  the  closed-chain  hydrocarbons. 

Ethyl  mercaptan,  also  called  thioalcohol,  C2H5SH,  is  a  type 
of  this  class.  It  is  a  colorless  liquid  used  in  the  preparation  of 
sulphonal. 

The  mercaptans  may  be  prepared  by  action  of  KHS  on  the 
alkyl  haloids: 

C2H5CI  +  KHS  =  C2H5SH  +  KCl. 

Taurine  is  an  important  sulphonic  acid  of  the  paraffin 
series.     Its  graphic  formula  shows  it  to  be  an  amino  ethyl  sul- 

/HSO3 
phonic  acid    C2H4  .     Taurine  is  derived  from  taurocholic 

^NH2 
acid  by  hydrolysis.     This  acid  is  representative  of  one  of  the  two 
principal  acid  groups  occuring  in  the  bile,  the  salts  of  which  may 
be  found  in  pathologic  conditions  in  the  urine,  or,  according  to 
Dr.  J.  P.  Michaels  and  others,  in  the  saliva. 

Nitro-benzene,  C6H5NO2,  may  be  produced  by  treating  ben- 
zene with  a  mixture  of  nitric  and  sulphuric  acid  at  reduced 
temperature.  (Exp.  no,  page  251.)  It  is  a  yellow,  oily  liquid, 
with  the  odor  of  bitter  almonds,  commercially  known  as  oil  of 
mirbane,  and  used  in  the  manufacture  of  aniline. 

Phenyl  Sulphuric  Acid,  C6H5HSO4,  occurs  only  in  combina- 
tion, the  acid  being  unstable  if  attempt  is  made  to  isolate  it. 
Its  potassium  salt  is  present  in  the  urine  as  a  product  of  in- 
testinal putrefaction. 


246  ORGANIC  CHEMISTRY 

Aniline  or  Amino-benzene,  C6H5NH2.  By  reaction  of  nitro- 
benzene with  nascent  hydrogen,  the  NO2  group  becomes  an  NH2 
group  and  aminobenzene  or  aniline  is  produced.  Aniline,  a  color- 
less liquid,  also  called  aniline  oil,  is  important  from  a  commercial 
rather  than  from  a  medical  standpoint,  as  it  forms  the  basis  of 
the  aniline  dyes.  When  pure  it  is  a  colorless  liquid,  but  changes 
quite  rapidly  when  exposed  to  the  light.  It  is  used  in  testing  for 
chloral  and  chloroform.  It  is  slightly  soluble  in  water,  and 
easily  soluble  in  alcohol  and  ether.  At  8°  C.  it  becomes  a  crys- 
talline solid. 

Cresol,  C3H4CH3OH,  is  a  hydroxy-toluene.  Three  isomeric 
compounds  of  this  formula  are  obtained  from  the  distillation  of 
coal  tar  between  200°  and  2 10°  C.  The  ortho  and  para  cresols  are 
solid  at  ordinary  temperatures,  the  ortho  compound  melting  at 
31°  C,  the  para  at  36°  C.  Meta  cresol  is  a  liquid  which  does 
not  solidify  unless  under  extreme  conditions  of  cold  and  pressure. 

The  cresols  are  similar  to  phenol  not  only  in  composition  but 
also  in  physical  and  therapeutic  properties ;  hence,  creso]  has  been 
called  cresylic  acid,  just  as  phenol  has  been  called  carbolic  acid. 

A  mixture  of  the  cresols,  said  to  be  composed  of  meta  cresol 
40%,  ortho  35%,  and  para  cresol  25%,  constitutes  the  tricresol 
very  largely  used  in  dentistry  as  a  germicide  and  antiseptic  sim- 
ilar to  carbolic  acid. 

An  emulsion  of  cresol,  obtained  by  the  solution  of  resin  soap 
as  an  emulsifying  agent,  is  known  as  creolin.  Cresol  is  also  a 
constituent  of  the  disinfectant  lysol. 

Tricresol  is  miscible  with  formalin  in  all  proportions,  and  the 
mixture  is  recommended  in  the  treatment  of  root  canals. 

Picric  Acid  is  trinitrophenol,  C6H2.0H.(N02)3.  It  may  be 
formed  by  action  of  strong  HNO3,  or  mixture  of  H2SO4  and 
HNO3  on  phenol.  It  occurs  as  yellow  plates  slightly  soluble 
in  H2O,  easily  soluble  in  alcohol  and  ether,  and  is  used  in  Esbach's 
reagent  for  the  estimation  of  albumin  in  urine  and  as  an  alkaloidal 
precipitant. 


CLOSED-CHAIN  HYDROCARBONS  247 

Benzoic  Acid,  CeHsCOOH,  was  originally  produced  from  gum 
benzoin,  but  may  be  made  from  hippuric  acid  (q.  v.),  which 
(from  urine  of  horses)  formerly  constituted  a  commercial  source. 
It  is  chiefly  prepared,  however,  from  toluene;  it  crystalHzes 
in  colorless  plates  or  long  prismatic  crystals  (from  solution). 
It  is  sparingly  soluble  in  cold  water,  more  soluble  in  hot  water, 
easily  soluble  in  alcohol.  It  sublimes  and  is  inflammable,  burn- 
ing without  residue. 

Benzoates  of  sodium,  ammonium,  lithium,  and  lime  are  all 
used  in  medicine.  Benzoated  lard  is  prepared  by  digesting  gum 
benzoin  in  hot  lard.  This  is  much  used  as  a  base  for  ointments 
and  keeps  well. 

Benzaldehyd,  CeHs-CHO,  is  a  colorless  liquid,  soluble  in 
alcohol  and  ether,  and  sparingly  soluble  in  water.  The  U.  S.  P. 
oil  of  bitter  almonds  is  practically  benzaldehyd;  it  is  a  volatile 
oil,  very  poisonous,  and  upon  standing  deposits  benzoic  acid 
from  partial  oxidation. 

Salicylic  Acid,  orthohydroxybenzoic  acid,  C6H4-OH.COOH, 
is  a  white  crystalline  powder,  odorless,  irritating  to  mucous  sur- 
faces, soluble  in  alcohol  and  ether,  and  in  about  450  parts  of 
water  at  15°  C.  (U.  S.  D.).  SahcyHc  acid  may  be  made  by 
action  of  CO2  on  sodium  phenate  and  subsequent  decomposition 
of  the  sodium  salicylate.  By  heating  rapidly  the  acid  may  be. 
changed  into  phenol  and  CO2. 

Salicylates  have  been  used  to  considerable  extent  in  various 
uric-acid  diseases.  Methyl  sahcylate  constitutes  90%  of  natu- 
ral oil  of  wintergreen  (page  207).  The  alcohoHc  solution  is 
essence  of  checkerberry. 

Salol  is  phenylsaHcylate,  C6H40H.COO(C6H5),  a  white 
crystaUine  powder,  practicafly  insoluble  in  water  and  not  de- 
composed by  the  dilute  acids  of  the  stomach  juices;  but  in  the 
intestine  it  becomes  salicyHc  acid  and  phenol,  as  follows: 

C6H4.OH.COOC6H5  +  H2O  =  C6H4OH.COOH  -f-  CeHsOH. 


248  ORGANIC  CHEMISTRY 

/HSO3 
Sulphanilic  acid,  C6H4  ,  is  isomeric  with  taurine,  but 

is  obtained,  however,  from  an  entirely  different  source.  It  is 
made  by  treating  aniline  with  concentrated  sulphuric  acid.  It 
is  a  strong  acid,  occurring  as  white  crystals,  is  soluble  in  water, 
and  is  used  in  the  manufacture  of  aniline  dyes  and  also  with 
naphthylamin  as  a  reagent  for  the  detection  of  nitrites. 

/COOH 
Phthalic  acid,  C6H4  ,  occurs  in  the  form  of  rhombic 

^COOH 
crystals.     By  heating  phthahc  acid,  phthalic  anhydrid  may  be 
obtained. 

PhthaHc  anhydrid,  C6II4  O,  heated  with  phenol  and 

II2SO4  will  give  phenolphthalein,  a  valuable  and  famiHar  indi- 
cator in  volumetric  analysis. 

Hippuric  Acid,  benzoyl  glycocoll,  C6H5.CO.NH.CH2-COOH, 
occurs  in  traces  in  human  urine,  to  a  considerable  extent  in 
the  urine  of  the  herbivora,  but  not  at  all  in  that  of  the  car- 
nivora.  It  crystallizes  in  prismatic  needles  (Plate  V,  Fig.  4), 
often  resembling  crystals  of  ammonium  magnesium  phosphate; 
but  as  these  latter  only  occur  in  neutral  or  alkaline  urine  and 
hippuric  acid,  usually  in  acid  urine,  there  is  little  danger  of 
confounding  the  two  substances.  Hippuric  acid  is  hydrolyzed 
by  the  urease  of  fermenting  urine,  forming  benzoic  acid  and 
glycocoll  (amino-acetic  acid) : 

C6H5CO-NH-CH2-COOH+H2O 

=  C6H5COOH+CH2NH2COOH. 

Tryosin,  C6H4.0H.-CH2CH(NH2)-COOH,  may  be  crystal- 
Hzed  as  fine  silky  needles.  It  is  formed  from  protein  sub- 
stances, particularly  casein  and  fibrin,  both  by  the  action  of 
proteolytic  enzymes  and  by  putrefactive  processes.     It  rarely 


CLOSED-CHAIN  HYDROCARBONS  249 

occurs  in  urinary  sediment;  when  found  it  is  in  bundles  or 
sheaves  (Plate  V,  Fig.  6,  page  222),  and  is  usually  indicative  of 
acute  liver  disease,  phosphorus  poisoning,  etc. 

Heterocyclic  Compounds.  —  The  closed-chain  or  cyclic  com- 
pounds are  known  as  isocycHc  or  homocyclic  when  the  atoms, 
constituting  the  "ring"  or  nucleus  of  the  molecule  are  all  of 
the  same  sort  (carbocycHc,  if  all  of  carbon),  as  has  been  the  case 
in  all  the  aromatic  compounds  which  we  have  thus  far  taken 
up,  i.e.,  the  structure  of  compounds  has  been  based  upon  the  six- 
carbon  or  benzene  ring.  If  the  ring  is  made  up  of  atoms  of 
different  sorts  the  compound  is  heterocyclic,  and  one  or  two  of 
these  are  of  importance. 

First,  pyridin,  C5H5N,  which  may  be  regarded  as  benzene,  in 
which  one  CH  group  has  been  replaced  by  an  atom  of  nitrogen :; 

H 

HC       CH 

i         11 
HC       CH 

It  is  a  liquid  miscible  with  water,  boiling-point  115°  C. 
Second,  quinalin,  C9H7N,  a  colorless  liquid. 

H        H 

HC        C        CH 

I         I  II 

HC        C        CH 

^C^^^N^ 
H 

Upon  one  or  the  other  of  these  two  bases  may  be  constructed 
the  graphic  formula  of  many  of  the  vegetable  alkaloids. 

A  certain  number  of  alkaloids,  such  as  caffein  and  thein  (tri- 
methylxanthin),  are  referable  to  the  purin  nucleus  (page  235). 


250  ORGANIC  CHEMISTRY 

H 

HC        C CH 

Indol,  C8H7N,  —     I  II         II     ,  —  is  produced  from  pro- 

HC        C        CH 

H         H 

tein  by  tlie  putrefaction  occurring  in  the  small  intestine,  also  by 
action  of  the  proteolytic  enzyme  of  the  pancreatic  juice  (trypsin) . 
The  indol,  by  oxidation  (after  absorption  from  the  intestines), 
becomes  indoxyl,  CsHeNO,  which,  with  K2SO4,  forms  indoxyl- 
potassium  sulphate,  C8H6NKSO4,  and,  as  such,  is  eliminated  (in 
part)  by  the  kidneys.  This  substance  is  a  type  of  the  so-called 
ethereal  or  conjugate  sulphates,  skatoxyl-potassium  sulphate 
(skatol)  and  phenol-potassium  sulphate  being  other  com- 
pounds of  this  class.  The  ethereal  sulphates  are  not  precipi- 
tated by  BaCl2  in  alkaHne  solutions,  but  may  be  decomposed  by 
prolonged  boihng  with  HCl  and  then  precipitated  as  usual. 

The  oxidation  of  indoxyl  produces  indigo  blue,  and  this  fact 
is  utilized  in  the  qualitative  test  for  indoxyl  in  urine  (q.  v.). 

/  C.CH3   -^^  ... 

Skatol,  methylindol,  C6H4  ^  ^  CH,  occurs  m  similar 

\NH/ 

manner  to  indoxyl,  and  likewise  passes  into  the  urine  as  an 
ethereal  sulphate  (skatoxyl-potassium  sulphate).  Skatol  is  a 
constituent  of  the  feces  and  possesses  a  strong  fecal  odor. 

Laboratory  Exercises  LIX  and  LX. 
Experiments  with  Aromatic  Hydrocarbons. 

Exp.  108.  Into  a  small  and  thoroughly  dry  flask  (250  c.c.) 
introduce  about  50  grams  of  a  mixture  consisting  of  i  part  of 
benzoic  acid  and  2  parts  of  quickHme ;  connect  with  a  condenser 
and  heat.     Benzene  (benzol)  distils  over: 

CaO  +  CeHsCOOH  =  CaCOa  +  CeHe. 


CLOSED-CHAIN  HYDROCARBONS  251 

Exp.  109.  Turn  a  little  of  the  benzene  prepared  in  the  last 
experiment  onto  some  water  contained  in  a  porcelain  capsule. 
Set  fire  to  it  and  note  that  it  burns  with  a  smoky  flame.  Cool  a 
few  cubic  centimeters  of  pure  benzene  contained  in  a  narrow 
test-tube  by  immersion  in  a  freezing  mixture  of  ice  and  salt. 

Exp.  no.  In  a  wide  test-tube  mix  5  c.c.  of  concentrated 
H2SO4  with  about  half  its  volume  of  strong  HNO3;  cool  in  ice- 
water  or  cold  running  water,  and  add  very  slowly  about  2  c.c. 
of  benzene.  Nitrobenzene  is  formed  and  may  be  separated  as 
a  heavy  oily  liquid  by  pouring  the  mixture  into  an  excess  of 
water.     Notice  the  odor  of  oil  of  bitter  almonds. 

Exp.  III.  Observing  the  same  precaution  against  overheat- 
ing as  given  in  Exp.  no  reduce  nitrobenzene  to  amino  benzene 
as  follows:  In  a  large  test-tube  or  small  flask  place  i  or  2  c.c. 
of  nitrobenzene  with  three  times  its  weight  of  tin  powder.  To 
this  add  10  or  15  c.c.  of  strong  HCl  in  successive  small  portions, 
keeping  cool  as  indicated.  The  odor  of  nitrobenzene  should  be 
replaced  by  that  of  aniline. 

Exp.  112.  Shake  together  in  a  test-tube  i  part  of  aniline  oil 
and  5  parts  of  water.     Is  the  oil  soluble  in  water? 

Agitate  with  HCl  added  in  small  portions  till  Hquid  becomes 
clear.     Explain. 

Exp.  113.  To  a  few  cubic  centimeters  of  a  3%  phenol  solu- 
tion add  dilute  bromin  water.  A  yellowish-white  crystalline 
precipitate  of  tribromphenol  is  produced  (see  page  1 74) . 

Exp.  114.  To  an  aqueous  solution  of  phenol  add  a  few 
drops  of  solution  of  ferric  chlorid. 

Exp.  115.  Produce  a  tribromaniline  according  to  method 
given  for  tribromphenol  in  Exp.  113. 

Exp.  116.  Repeat  Exps.  113  and  114,  using  an  aqueous  solu- 
tion of  cresol  in  place  of  phenol. 

Exp.  117.  To  a  test-tube  1/3  full  of  nitric  acid,  (50%  abso- 
lute HNO3),  add,  I  drop  at  a  time,  about  i  c.c.  of  phenol  with 
constant  agitation.     When  the  phenol  has  all  been  added  heat 


252  ORGANIC  CHEMISTRY 

carefully  to  boiling.  Allow  to  cool  slowly  when  trinitrophenol 
will  be  precipitated. 

Exp.  ii8.  Evaporate  a  few  drops  of  a  i%  solution  of  potas- 
sium nitrate  to  dryness  in  a  small  porcelain  capsule.  Add  2  c.c.  of 
phenoldisulphonic  acid ;  *  stir  thoroughly,  and  keep  hot  for  three 
to  five  minutes;  dilute  with  water,  make  strongly  alkaHne  with 
ammonia,  and  note  the  intense  yellow  color  of  ammonium  picrate. 
The  reaction  is  used  as  a  test  for  nitrates  in  drinking  water, 

Exp.  119.     Determine  melting-point  of  benzoic  acid. 

Exp.  120.  Arrange  two  watch  glasses  of  equal  size  with  the 
concave  surfaces  together  and  a  piece  of  filter  paper  stretched 
between  them.  The  glasses  may  be  held  together  with  a  small 
brass  clamp. 

A  little  benzoic  acid  placed  in  the  lower  glass  may  be  sub- 
limed by  means  of  a  gentle  heat  through  the  paper  and  collected 
upon  the  upper  glass.  Examine  the  sublimate  by  polarized 
light.     See  Plate  V,  Fig.  5,  opposite  page  222. 

Exp.  121.  With  an  aqueous  solution  of  benzaldehyd  deter- 
mine whether  Tollen's  test  for  aldehyds  (Exp.  64,  page  201)  is 
appUcable  to  aromatic  compounds. 

Exp.  122.  Boil  10  c.c.  of  oil  of  wintergreen  with  a  Httle  of  20% 
NaOH ;  keep  the  volume  constant  by  frequent  addition  of  water. 
When  the  oil  has  entirely  disappeared,  cool  and  add  HCl  to  acid 
reaction.     SaHcyUc  acid  will  separate,  white  and  crystalline. 

Exp.  123.  To  a  dilute  solution  of  sodium  saHcylate,  or  satu- 
rated aqueous  solution  of  salicylic  acid,  add  a  few  drops  of 
FegCle.  A  slight  amount  of  saHcylates  in  the  urine  will  produce 
this  color  when  a  test  is  being  made  for  diacetic  acid  (q.  v.) 

Exp.  124.  Mix  in  a  test-tube  a  Httle  dry  slaked  lime  and 
salicyKc  acid,  heat  and  collect  a  few  drops  of  distillate  in  a 
second  tube.     Test  distillate  for  phenol.     Write  reaction. 

Note.  —  After  the  first  heating,  the  tube  containing  the  lime  and  acid  may  be 
inclined  so  that  any  moisture  distillate  will  run  into  collecting  tube  rather  than 
back  onto  the  mixture. 

*  For  method  of  preparation  of  phenoldisulphonic  acid,  see  Appendix. 


PART   VI. 

PHYSIOLOGICAL  CHEMISTRY. 


CHAPTER  XXIX. 

FERMENTS   OR   ENZYMES. 

Physiological  chemistry  treats  of  the  substances  which  go 
to  make  up  the  animal  body,  the  changes  which  these  substances 
undergo  in  the  process  of  digestion  and  assimilation,  and  the  final 
products  of  metabolism. 

This  subject,  like  others,  will  receive  our  attention  in  out- 
Hne,  with  a  view  simply  to  enable  the  student  to  understand 
the  conditions  which  at  present  seem  to  have  the  most  direct 
bearing  on  dental  science.  The  changes  produced  by  the  class 
of  bodies  known  as  ferments  are  of  great  importance  and  the 
first  to  be  considered. 

If  yeast  is  allowed  to  grow  in  a  sugar  solution  of  moderate 
strength,  the  sugar  molecule  is  spKt  into  carbonic-acid  gas  and 
alcohol.  The  process  is  one  of  fermentation;  the  yeast  is  the 
ferment.  There  are  various  substances  which  cause  similar 
sphtting  of  complex  molecules  into  simpler  compounds.* 

The  distinction  between  the  organized  and  the  unorganized 
ferments  is  no  longer  recognized,  as  it  has  been  proved  that  the 
activity  of  an  organized  ferment  is  due  to  the  presence  of  the 
unorganized  ferment  or  enzyme,  and  we  shall,  by  preference, 
refer  to  these  substances  as  enzymes. 

The  enzymes,  as  a  class,  possess  certain  general  properties 
which  should  be  remembered. 

*  Occasionally  fermentation  may  produce  a  synthesis  (putting  together)  rather 
than  an  analysis  (pulling  apart). 

253 


254  PHYSIOLOGICAL  CHEMISTRY 

First.  Their  action  is  limited  to  a  very  few  substances; 
i.e.,  the  enzyme  from  yeast,  referred  to  above,  will  convert  a 
few  sugars  only  as  indicated.  They  will  not  act  in  any  other 
way  nor  upon  other  substances. 

Second.  The  enzymes  act  only  at  ordinary  temperatures, 
usually  showing  the  greatest  activity  at  about  the  temperature 
of  the  animal  body,  37°  to  40°  C. 

Third.  Enzymes  act  only  within  very  narrow  limits  as  re- 
gards the  chemical  reaction  (acid  or  alkaline)  of  the  media. 

Fourth.  Enzymes  are  destroyed  (killed)  by  the  heat  of  boil- 
ing water. 

Fifth.  In  regard  to  the  nature  of  their  composition,  many  of 
the  enzymes  are  closely  allied  to  the  proteins. 

An  enzyme  may  be  classified  according  to  the  sort  of  work 
it  does.  Many  of  the  chemical  changes  involved  in  the  utiliza- 
tion of  food  consist  of  breaking  up  a  complex  molecule  and  by 
the  use  of  a  molecule  of  water  forming  new  and  simpler  com- 
pounds. This  sort  of  change  is  called  "Hydrolysis"  and  an 
enzjnne  which  will  produce  it  is  a  hydrolytic  enzyme.  By 
hydrolysis  or  hydrolytic  cleavage,  the  molecule  of  cane-sugar, 
C12H22O11,  becomes  two  molecules  of  a  simpler  sugar,  such  as 
glucose,  C6H12O6.     C12H22O11  +  H2O  =  2  C6H12O6. 

Hydrolysis  is  not  dependent  upon  enzyme  action,  as  the 
same  change  is  produced  by  prolonged  boiling  with  very  dilute 
mineral  acids. 

Besides  the  classification  of  enzymes  by  the  character  of  the 
work  they  do,  the  name  of  the  substance  acted  upon  may  also 
be  used  to  designate  an  enzyme;  thus,  a  proteolytic  enz5mie 
produces  a  cleavage  of  protein  substances.  A  lipolytic  enzyme 
(lipase)  splits  the  fat  molecule,  etc. 

Several  of  the  digestive  enzymes,  notably  the  proteolytic  or 
flesh-digesting  enzymes,  such  as  pepsin,  trypsin,  etc.,  exist  in 
the  animal  cell,  not  as  active  agents,  but  as  inactive  parent 
enzyxQes  which  are  called  pro-enzymes  or  zymogens.     Enz3mies 


FERMENTS  OR  ENZYMES  255 

of  this  class  are  set  to  work  (liberated  from  the  parent  sub- 
stance) by  a  class  of  substances  known  as  "activators"  (illus- 
trated by  the  enterokinase  of  the  intestine,  p.  337). 

Neither  the  zymogen  nor  the  activator  has  of  itself  any  diges- 
tive action  whatever.  A  provision  which  results  in  the  preven- 
tion of  autodigestion  (autolysis)  of  the  cells  containing  them. 

Another  large  and  very  important  class  of  enzymes  are  those 
which  produce  oxidative  changes.  They  may  be  divided  into 
the  oxidases,  which  produce  direct  oxidation,  and  the  peroxidases, 
which  produce  oxidation  only  in  the  presence  or  by  the  aid  of 
peroxide. 

Catalase  is  a  term  which  has  been  applied  to  enzymes, 
similar  in  action  to  the  peroxides;  i.e.,  they  destroy  a  peroxide 
with  the  formation  of  molecular  oxygen,  although,  according  to 
Hammarsten,  they  differ  from  both  the  oxidases  and  peroxidases 
in  giving  no  reaction  whatever  with  Guaiac. 

Oxidases  have  been  found  to  exist  in  saliva,  in  milk,  blood, 
nasal  mucus,  tears,  and  semen,  in  many  of  the  organs,  and  also 
in  the  muscular  tissue.  They  exist  moreover  in  the  vegetable 
kingdom  from  which  the  subject  of  oxidizing  enzymes  was  first 
studied  by  Bertrand  and  Bourquelot.*  The  urine,  bile  and  intes- 
tinal secretions  are  said  not  to  contain  a  ferment  of  this  kind. 

The  name  of  a  specific  enzyme  usually  ends  in  "-ase"  as 
zymase,  the  enzyme  contained  in  yeast;  Hpase,  a  fat-spHtting 
enz3niie;  urease,  the  urine  ferment. 

Laboratory  Exercise  LXI. 

Preparation  of  Oxidase. 

Exp.  125.  Clean  thoroughly  a  small  potato  and  grate  the 
skin  into  a  small  beaker;  cover  with  water  and  allow  to  stand 
in  a  cool  place  for  an  hour.     Filter  through  coarse  paper.     Turn 

*"Enz3rmes  and  their  Applications,"  Effrant:  Prescott's  translation.  This 
work  is  also  authority  for  statement  immediately  preceding  regarding  the  source 
of  oxydizing  enzymes. 


256 


PHYSIOLOGICAL   CHEMISTRY 


about  5  c.c.  of  the  filtrate  slowly  into  25  c.c.  of  strong  alcohol. 
The  enzyme  will  be  precipitated.     Filter  and  test  as  follows: 

Exp.  126.  Transfer  the  moist  precipitate  from  the  above  ex- 
periment into  a  half  a  test  tube  of  distilled  water.  Shake  fre- 
quently for  about  10  minutes  and  filter.  The  filtrate  will  con- 
tain oxidizing  enzymes  in  solution.  Divide  the  solution  into 
two  parts ;  to  one  add  a  few  drops  of  tincture  of  guaiacum,  and 
to  the  other  a  little  of  a  1%  solution  of  pyrocatechol.  The 
guaiacum  gives  a  blue  color,  and  the  pyrocatechol  a  red-brown 
color  in  the  presence  of  oxidizing  enzymes. 

Experiments  with  Enzymes. 

Hydrolytic  enzymes  produce  cleavage  of  the  molecule. 

Exp.  127.     Take    five  test  tubes,    "a-b-c-d-e."     Make  a 

thin  paste  by  rubbing  one-sixth  of 
a  yeast  cake  with  water,  and  place 
a  little  in  each  of  the  five  tubes; 
then  fill  "a"  with  a  dilute  glucose 
solution;  ^'b  "  with  a  dilute  solution 
of  milk  sugar;  "c"  with  dilute 
solution  of  cane  sugar;  to  "d" 
add  a  little  invertase  (an  enzyme 
from  the  mucosa  of  the  small  in- 
testine of  a  pig)  (see  Appendix); 
then  fill  with  the  same  solution 
used  for  *'c".  Prepare  "e"  ex- 
actly the  same  as  "d"  except  that 
before  adding  the  sugar  solution 
the  enzymes  are  boiled  for  at  least 
one  minute.  Fit  each  tube  with 
short  delivery  tube  and  allow  to 
stand  overnight. 

Arrange  as  indicated  in  Fig.  16.     Explain  result  in  each  case. 

Exp.  128.     Take  four  test-tubes,  "a-b-c-d,"  and  half  fill 


Fig.  16. 


FERMENTS  OR   ENZYMES  257 

each  with  some  thin  starch  paste  (see  page  383  of  Appendix). 
Into  "a"  put  a  little  of  the  yeast  from  last  experiment;  into 
"b"  a  Httle  pepsin  solution;  into  "c"  a  Httle  saliva  (the  enzyme 
of  the  saliva  in  ptyalin);  into  ''d"  a  little  invertase  as  used  in 
preceding  experiment.  Warm  all  the  tubes  to  about  37  or 
38°  C,  and  allow  to  stand  overnight;  then  test  contents  of 
each  tube  for  a  reducing  sugar  which  may  have  been  produced 
from  the  starch.     (Use  Exp.  136,  page  262). 

Exp.  129.  If  time  and  sufficient  material  are  available,  the 
student  may  prepare  a  fat-spKtting  enzyme  (Hpase)  from  an 
animal  source,  pigs,  pancreas,*  or  from  a  vegetable  source,  castor 
beans.* 

Exp.  130.  To  one-third  of  a  test-tube  of  milk,  colored 
shghtly  blue  with  nearly  neutral  Ktmus  solution,  add  half  as 
much  solution  of  hpase  (fresh  pancreatic  extract)  and  keep  at 
about  40°  C.  for  twenty  to  thirty  minutes.  Sufficient  fat  acid 
should  be  separated  to  change  the  blue  htmus  to  red.  Write 
reaction. 

*  For  preparation  of  lipase  see  Appendix,  pages  380  and  381. 


CHAPTER  XXX. 


Classification : 


Sugars 


CARBOHYDRATES. 

Arabinose 


Xylose 

Dextrose 
Leevulose 
Galactose 


Pentoses. 


Monosaccharids  or  monoses. 


Starch 


Saccharose  ] 

Maltose        >  Disaccharids  or  dioses. 

Lactose  J 
( Starch  "] 
(  Glycogen 


Gum 
Cellulose 


■    Polysaccharids  or  polyoses. 


1  Dextrin 


Characteristics.  —  The  monosaccharids  are  reducing  bodies  of 
either  the  aldehyd  or  the  ketone  type.  The  termination  "ose" 
is  applied  to  all  sugars,  and  may  also  be  used  in  designating  the 
type;  thus  dextrose  is  an  "aldose, "  while  laevulose  is  a  ''ketose;" 
i.e.,  dextrose  is  an  aldehyd,  containing  the  characteristic  -CHO 
group,  while  Laevulose  is  a  ketone  containing  the  -C  =  0 
group. 

The  pentoses  (C5H10O5)  are  represented  by  two  important 
compounds,  arabinose  and  xylose.  The  first  of  these  occurs 
occasionally  in  the  urine  (pentosuria),  and  can  be  prepared  by 
boiling  gum  arable  with  dilute  mineral  acids.  The  second, 
xylose,  has  been  obtained  from  the  pancreas,  but  may  be  pre- 
pared more  easily  from  bran  or  straw  by  boiling  with  dilute 
HCl  (Exp.  131,  page  261). 

258 


CARBOH  YDRA  TES  259 

The  pentoses,  as  a  class,  boiled  with  dilute  mineral  acid 
(HCl  or  H2SO4) ,  yield  f urfuraldehyd  by  splitting  off  the  elements 
of  three  molecules  of  water: 

C5H10O5  -  3  H2O  =  C5H4O2. 

The  formation  of  furfuraldehyd  can  be  easily  demonstrated 
by  various  color  reactions  as  given  in  experiment  131,  page  261. 

The  hexoses,  C6H12O6,  also  called  monoses,  occur  quite  gen- 
erally in  nature  (not  true  of  the  pentoses).  They  constitute  the 
various  fruit  sugars,  and  may  be  obtained  by  hydrolysis  of  the 
dioses  and  polyoses. 

They  all  reduce  FehHng's  copper  solution  (galactose  less 
easily  than  the  others),  and  they  are  all  fermented  by  yeast 
(galactose  more  slowly  than  the  others). 

Dextrose  or  Glucose,  C6H12O6,  also  known  as  grape-sugar 
and  as  diabetic  sugar,  occurs  in  grapes,  honey,  etc.  It  is  formed 
by  the  action  of  diastatic  ferments  on  the  disaccharids ;  also 
from  many  of  the  polysaccharids.  Glucose  thus  occurs  in  the 
processes  of  digestion  and  constitutes  the  sugar  of  diabetic 
urine.  It  may  be  obtained  commercially  as  a  white  solid,  and 
also  as  a  thick,  heavy  syrup,  known  as  confectioners'  glucose. 
The  commercial  glucose  is  prepared  by  the  action  of  dilute  acids 
on  starch,  when  hydrolysis  takes  place,  as  follows: 
CeHioCs  +  H2O  =  C6II12O6. 

Dextrose  can  be  oxidized  first  to  gluconic  acid  (CH2OH.- 
(CH0H)4.C00H),  and  by  further  oxidation  to  dibasic  sac- 
charic acid: 

C00H.(CH0H)4.C00H. 

This  oxidation  can  be  effected  by  the  use  of  nitric  acid.  Sac- 
charic acid  forms  a  definite  soluble  salt  with  calcium.  Whether 
the  fact  has  any  bearing  whatever  on  the  relation  of  poor  teeth 
and  excessive  use  of  candy  has  not  been  demonstrated. 

Tests.  —  Glucose  boiled  with  Fehling's  solution  precipitates 
the  red  suboxid  of  copper  (CU2O). 


26o  PHYSIOLOGICAL  CHEMISTRY 

Glucose  responds  to  Molisch's  test  for  carbohydrates,  which 
is  made  with  an  alcoholic  solution  of  a-naphthol  and  concen- 
trated sulphuric  acid.  (Exp.  133.)  It  may  be  distinguished 
not  only  from  other  carbohydrates  but  from  other  sugars  by 
heating  with  Barfoed's  solution  (copper  acetate  in  dilute  acetic 
acid),  which  is  reduced  with  precipitation  of  CU2O. 

Heated  with  phenylhydrazine  solution  nearly  to  the  boiling- 
point  of  water,  glucose  forms  phenylglucosazone,  which  crystal- 
lizes, as  the  mixture  cools,  in  characteristic  yellow  needles 
usually  arranged  in  bundles  or  sheaves.     (Plate  VI,  Fig.  i.) 

Osazones  are  the  various  compounds  formed  by  the  different 
sugars  and  phenylhydrazine  when  treated  as  above.  They 
crystallize  in  fairly  distinctive  forms  and  furnish  valuable  tests 
for  the  sugars.  The  phenylhydrazine  test  is  considered  at  least 
ten  times  more  delicate  than  Fehhng's  test.  Glucose  readily 
undergoes  alcohohc  fermentation,  yielding  C2H5OH  and  CO2. 
(See  Exp.  140,  page  262.) 

Laevulose,  C6H12O6,  or  fruit-sugar,  turns  the  ray  of  polarized 
light  to  the  left,  and  to  a  greater  degree  than  glucose  turns  it  to 
the  right.  It  occurs  in  honey  and  in  many  fruits,  and  is  pro- 
duced with  glucose  by  hydrolysis  of  cane-sugar.  Laevulose 
forms  an  osazone  not  to  be  distinguished  from  glucosazone.  It 
reduces  copper  solutions  in  a  manner  similar  to  glucose,  and,  like 
it,  is  easily  fermented  by  yeast. 

Galactose  is  the  product  of  the  hydrolysis  of  lactose,  or  milk- 
sugar,  and  some  other  carbohydrates.  It  is  a  crystalline  sub- 
stance which  reduces  Fehhng's  solution  and  ferments  slowly 
with  yeast. 

DiSACCHARIDS   OR   DiOSES. 

Disaccharids  have  the  general  formula  C12H22O11.  They 
are  converted  into  the  monosaccharids  by  hydrolysis  brought 
about  either  by  action  of  enzymes  or  by  boiling  with  mineral 
acid. 


PLATE  VI.— PHYSIOLOGICAL   CHEMISTRY 


Fig.  I. 
Glucosazone. 


Fig.  3. 
Lactosazone. 


Fig.  2. 
Maltosazone. 


Fig.  4. 

Wheat  Starch. 


Fig.  5. 
A,  Com  starch;  B,  Rice  starch. 


Fig.  6. 
.4,  Potato  starch;  B,  Arrowroot  starch. 


CARBOHYDRATES  261 

Cane-sugar,  C12H22O11,  sucrose  or  saccharose,  obtained  from 
the  sugar-cane  (various  varieties  of  sorghum),  also  from  the 
sugar-beet  {Beta  vulgaris)  and  the  sugar-maple  {Acer  saccha- 
rinum).  Cane-sugar  is  a  white  crystalHne  solid  soluble  in  about 
1/2  part  of  water  and  in  175  parts  of  alcohol  (U.  S.  P.).  It  does 
not  reduce  copper  solutions,  nor  does  it  form  an  osazone  with 
phenylhydrazine ;  but  it  is  easily  hydrolyzed  with  the  formation 
of  dextrose  and  laevulose,  and  then,  of  course,  the  reactions 
peculiar  to  these  substances  may  be  obtained.  It  does  not  fer- 
ment directly,  but,  by  the  action  of  invertin  contained  in  yeast, 
it  takes  up  water,  becoming  glucose  and  laevulose  as  above,  these 
latter  sugars  being  easily  fermentable. 

Maltose,  C12H22O11,  or  malt-sugar,  is  an  intermediate  prod- 
uct in  the  hydrolysis  of  starch,  and  by  further  hydration  be- 
comes two  molecules  of  dextrose:  C12H22O11  -f  H2O  =  2  C6H12O6. 
It  is  formed  in  the  fermentation  of  barley  by  diastase  (the  fer- 
ment of  malt),  and  with  phenylhydrazine  it  produces  an  osazone 
distinguished  from  glucosazone  and  lactosazone  by  its  micro- 
scopical appearance  (Plate  VI,  Fig.  2)  and  its  melting-point. 

Lactose,  Ci2H220n,  obtained  from  milk,  is  a  disaccharid 
with  far  less  sweetening  power  than  sucrose.  It  forms  an 
osazone  which  crystalHzes  in  small  burr-shaped  forms  (Plate  VI, 
Fig.  3).  It  reduces  Fehling's  solution,  but  does  not  reduce 
Barfoed's  solution.  It  resists  fermentation  in  a  marked  de- 
gree. Upon  hydration  it  is  converted  into  dextrose  and  galac- 
tose. 

Laboratory  Exercise  LXII. 

Experiments  with  Sugars. 

Exp.  131.  Fill  a  test-tube  about  one- third  full  of  dry  straw. 
Cover  with  10%  hydrochloric  acid;  boil,  collecting  the  distillate 
in  a  dry  tube.  Divide  the  distillate  into  two  parts,  and  make 
the  following  tests  for  furfuraldehyd  which  has  been  produced 
from  the  pentose  contained  in  the  straw.     Treat  the  contents 


262  PHYSIOLOGICAL   CHEMISTRY 

of  one  tube  with  a  little  aniline  and  HCl.  Red  coloration  indi- 
cates the  presence  of  furfuraldehyd.  To  the  contents  of  the 
other  tube  add  a  little  solution  of  casein  (skimmed  milk)  and  un- 
derlay with  strong  sulphuric  acid.  Furfurol  will  give  a  blue  or 
purple  line  at  the  point  of  contact  of  the  two  liquids. 

Monosaccharids.  —  Exp.  132.  Test  for  C  and  H,  using  cane- 
sugar.  Make  closed-tube  test  for  H,  which  is  given  off  as  H2O, 
and  for  C,  which  remains  as  such  in  tube.  (See  page  182.) 
Write  reactions. 

Exp.  133.  Molisch''s  Test  for  Carbohydrates. — To  a  few 
cubic  centimeters  of  a  3%  glucose  solution  add  a  few  drops  of 
an  alcoholic  solution  of  a-naphthol,  and  carefully  underlay  the 
mixture  with  strong  H2SO4. 

Exp.  134.  To  a  few  cubic  centimeters  of  CUSO4  solution 
in  a  test-tube  add  a  little  NaOH.     Boil  and  write  reaction. 

Exp.  135.  Repeat  Exp.  134  with  the  addition  of  Rochelle 
salt;  if  solution  remains  clear  on  boiling,  add  a  few  drops  of  a 
glucose  solution. 

Exp.  136.  Fehling's  Test  for  Sugars.  —  Take  about  5  c.c.  of 
Fehling's  solution*  made  by  mixing  equal  parts  of  the  CUSO4 
solution  and  the  alkaline  tartrate  on  side  shelf.  Boil  and  add 
immediately  a  few  drops  of  glucose  solution.  Set  aside  for  a 
few  minutes,  watching  the  results. 

Exp.  137.  Repeat  Exp.  136,  using  diabetic  urine  instead  of 
glucose. 

Exp.  138.  Repeat  Exp.  136  without  heat  and  allow  to  stand 
for  twenty-four  hours. 

Exp.  139.  Barfoed's  Test.  —  To  about  5  c.c.  of  Barfoed's 
reagent  add  a  few  drops  of  glucose  solution;  boil  and  set  aside 
for  a  few  minutes,  watching  results. 

Exp.  140.  Fermentation  Test.  —  Fill  the  "fermentation- 
tube"  (Fig.  17,  page  263)  found  in  the  desk  with  glucose  solu- 
tion;  add  a  little  yeast;  insert  stopper,  with  long  arm  of  tube 

*  For  preparation,  see  Appendix. 


CARBOHYDRATES 


263 


extending  into  glucose  mixture  nearly  to  bottom  of  tube,  and 
allow  it  to  stand  upright,  in  a  warm  place,  overnight.  On  the  next 
day,  test  the  gas,  with  which  the  tube  is  filled,  with  lime-water. 

Exp.  141.  Phenylhydrazine  Test. — Place  about  5  c.c  of 
glucose  solution  in  a  test-tube;  add  an  equal 
volume  of  phenylhydrazine  solution;  keep  the 
tube  in  boiling  water  for  thirty  minutes.  Allow 
to  cool  gradually.  Examine  the  precipitate  micro- 
scopically and  sketch  the  crystals. 

Disaccharids.  —  Exp.  142.  Use  dilute  solu- 
tions of  cane-sugar,  milk-sugar,  and  maltose, 
and  make  on  each  Fehling's  test  (Exp.  136), 
Barfoed's  test  (Exp.  139),  and  the  phenylhy- 
drazine test  (Exp.  141).  Sketch  the  different 
osazone  crystals  obtained. 

Exp.  143.  To  a  dilute  solution  of  cane-sugar 
add  a  few  drops  of  dilute  H2SO4  and  boil  for 
five  minutes.  Cool  the  mixture  and  make  slightly 
alkaline  with  NaOH.  With  this  solution  perform 
Exps.  136-139  and  141.  Explain  results.  Com- 
pare with  Exp.  142. 

POLYOSES  —  POLYSACCHARIDS. 

Starch.  —  This  well-known  and  widely  distributed  plant-con- 
stituent is  a  carbohydrate  represented  by  CeHioOs,  the  actual 
molecule,  however,  being  many  times  this  simple  formula.  The 
microscopical  appearance  of  the  starch  granule  is  quite  charac- 
teristic, and  recognition  of  the  more  common  starches  by  this 
method  is  not  at  all  difi&cult  (see  Plate  VI,  page  261). 

Starch  is  not  soluble  in  cold  water,  but  in  hot  water,  or  in 
solutions  containing  "amylolytic"  enzymes,  or  in  solutions 
containing  certain  chemical  substances,  as  chlorid  of  zinc  or  of 
magnesium,  dilute  HCl  or  H2SO4,  capable  of  forming  hydrolytic 
products,  the  starch  granules  swell  up,  and  ultimately  dissolve, 


Fig. 


17- 


264  PHYSIOLOGICAL   CHEMISTRY 

being  converted  into  dextrose.  The  conversion,  however,  takes 
place  in  several  well-defined  steps,  as  follows:  Soluble  starch 
is  first  formed,  answering  the  same  chemical  test  with  iodin 
(Exp.  214,  p.  328);  next,  erythrodextrin,  which  gives  a  red  color 
with  iodin  solution;  then  achroo-  and  maltodextrin,  which  give  no 
color  with  iodin,  but  react  slightly  with  Fehhng's  copper  solu- 
tion; then  maltose,  also  negative  with  iodin,  but  reacting  strongly 
with  Fehling's  solution;  and  finally  dextrose. 

Dextrin  (CeHioOs)  is  a  yellowish  powder,  also  known  as 
British  gum;  is  formed  from  starch,  as  indicated  above;  con- 
stitutes to  a  considerable  extent  the  "  crust"  of  bread;  is  solu- 
ble in  water,  the  solution  giving  a  red  color  with  iodin,  and  is 
also  distinguished  from  starch  by  its  failure  to  give  a  precipitate 
with  solution  of  tannic  acid. 

Glycogen,  or  animal  starch,  is  a  carbohydrate,  with  the  gen- 
eral formula  CeHioOs,  occurring  principally  in  the  Hver,  and  to 
a  lesser  extent  in  nearly  all  parts  of  the  animal  body.  Freshly 
opened  oysters  are  a  convenient  source  of  the  substance  for 
laboratory  demonstration.  It  occurs  in  horse-flesh  in  consider- 
ably larger  proportions  than  in  human  flesh. 

Properties.  —  Glycogen  is  a  white  powder  without  odor  or 
taste.  It  dissolves  in  water,  producing  an  opalescent  solution. 
It  is  closely  allied  to  the  starches  of  vegetable  origin  in  that  the 
products  of  its  hydrolysis  are  dextrin*  and  ultimately  dextrose. 
It  differs  in  its  ready  solubility  in  water,  and  in  the  fact  that 
it  is  precipitated  by  66%  alcohol,  also  in  its  power  of  rotation, 
which  is  much  stronger  than  that  of  starch. 

Physiology.  —  Glycogen  is  formed  by  the  liver,  and  stored  by 
this  same  organ  for  future  use.  It  is  derived  principally  from 
carbohydrates,  but  may  also  be  derived  from  proteins.  It  dis- 
appears during  starvation.  In  dead  liver  or  muscle  it  rapidly 
undergoes  hydrolytic  change  with  the  production  of  a  reducing 
sugar. 

*  Foster's  Text-book  of  Physiology. 


CARBOHYDRATES  26$ 

Cellulose,  CeHioOs,  is  a  carbohydrate  which  occurs  as  a 
principal  constituent  of  woody  fiber,  and  which  may  be  found 
in  the  laboratory  in  nearly  a  pure  state,  as  absorbent  cotton 
or  Swedish  filter-paper.  It  is  insoluble  in  water,  alcohol,  or 
dilute  acids;  it  may  be  dissolved,  however,  by  an  ammoniacal 
copper  solution.  It  is  converted  into  monosaccharids  by  acids, 
only  after  first  treating  with  concentrated  H2SO4,  which  par- 
tially dissolves  it.  Cellulose  aids  digestion  in  a  purely  mechan- 
ical way;  treated  with  a  mixture  of  nitric  and  sulphuric  acids, 
it  is  converted  into  nitro-substitution  products  which  are  known 
as  guncotton.  The  soluble  cotton  from  which  collodion  is  pre- 
pared is  a  mixture  of  tetra-  and  pentanitrates,  while  the  more 
explosive  but  insoluble  guncotton  is  a  hexanitrate,  formerly 
known  as  trinitrocellulose. 

Experiments  with  Starches  and  Cellulose. 

Polysaccharids.  —  Exp.  No.  144.  Examine  potato,  corn,  and 
wheat  starch  under  the  microscope,  use  a  drop  of  water  and  a 
cover  glass.  Sketch  the  granules  of  each  in  note-book,  and, 
while  still  on  the  slide,  treat  with  a  dilute  iodin  solution.  Note 
changes  in  appearance  of  granules. 

Exp.  145.  Preparation  of  starch.  Grate  a  little  raw  potato. 
Mix  thoroughly  with  water  and  strain  through  "bolting"  cloth 
or  stout  coarse  muslin.  After  the  liquid  has  run  through,  com- 
press the  cloth  by  twisting  till  no  more  liquid  can  be  squeezed 
out.  The  starch  has  passed  through  the  cloth  and  may  be  washed 
by  decantation,  dried  on  filter  paper,  examined,  and  used  for 
the  following  experiments: 

Exp.  146.  Make  some  starch  paste  by  rubbing  i  gram  of 
starch  to  a  smooth,  thin  paste  with  water ;  then  slowly  pour  it 
into  100  c.c.  of  boiHng  water,  stirring  constantly.  With  this 
solution  compare  a  1%  solution  of  dextrin  and  a  solution  of 
glycogen  *  as  follows : 

*  For  the  isolation  of  glycogen,  see  Appendix. 


266  PHYSIOLOGICAL  CHEMISTRY 

(a)  Treat  each  by  boiling  with  Fehhng's  solution. 

(b)  Add  to  5  c.c.  of  each  a  few  drops  of  tannic-acid  solu- 
tion. 

(c)  To  each  solution  add  a  drop  of  iodin  solution.  Note 
color  of  mixture  while  cold.  Heat  nearly  to  boihng  and  allow 
to  cool  again,  watching  the  color  during  process. 

(d)  To  5  c.c.  of  each  solution  add  twice  its  volume  of  66% 
alcohol. 

(e)  Tabulate  results  of  the  tests  and  formulate  method  of 
distinguishing  these  three  substances  from  one  another. 


CHAPTER  XXXI. 

FATS  AND   OILS. 

Natural  fats  and  oils  of  animal  or  vegetable  origin  are 
mixtures  of  several  compound  glyceryl  ethers  or  esters  (see  page 
209),  and  by  subjecting  them  to  cold  and  pressure  they  may 
be  separated  into  two  portions,  one  solid  with  comparatively 
high  melting-point,  and  the  other  Hquid  at  ordinary  tempera- 
tures. The  solid  portion  is  known  as  the  stearopten,  and  the 
liquid  as  the  eleopten,  of  the  fat.  Thus  from  beef-fat  we  may 
express  a  fluid  eleopten  consisting  largely  of  olein  and  obtain 
as  a  residue  a  stearopten,  stearin.  The  stearopten  of  the  vol- 
atile or  essential  oils  are  classed  as  camphors,  on  account  of 
their  resemblance  to  ordinary  camphor.  Menthol,  from  oil  of 
peppermint,  and  thymol,  from  oil  of  thyme,  are  examples  of  this 
class  of  compounds,  both  of  which  are  largely  used  in  dental 
practice. 

Properties.  —  Fats  are  insoluble  in  water,  easily  dissolved  by 
ether,  chloroform,  and  carbon  disulphid,  less  easily  by  alcohol, 
crystallizing  on  evaporation  of  the  solvent.  (Plate  VII,  Fig.  3, 
page  296.)  They  are  emulsified  by  mechanical  subdivision  of 
the  fat  globules,  in  the  presence  of  some  agent  which  prevents 
their  reuniting.  The  vegetable  mucilages,  soap,  jelly,  etc.,  are 
such  emulsifying  agents.  On  exposure  to  the  air,  fats  and  oils 
are  more  or  less  easily  oxidized,  which  causes  a  separation  of  the 
fat  acid.  This  produces  an  unpleasant  odor  or  taste,  and  the 
fat  is  said  to  become  rancid.  (For  saponification  of  fats  see 
page  209  and  Exp.  150,  page  268.) 

Physiology.  —  Fats  are  not  digested  to  any  appreciable  ex- 
tent until  they  reach  the  intestine;  here  they  are  broken  up 
by  a  fat-splitting  enzyme,  emulsified,  and  to  a  slight  extent 

267 


268  PHYSIOLOGICAL   CHEMISTRY 

saponified,  after  which  they  may  be  absorbed  by  the  system 
(see  Pancreatic  Digestion). 

Experiments  with  Fats  and  Oils. 

Exp.  147.  Test  solubility  of  olive-oil  in  water,  ether,  chloro- 
form, and  alcohol,  carefully  avoiding  the  vicinity  of  a  flame. 

Exp.  148.  Let  one  or  two  drops  of  an  ether  solution  of  the 
oil  drop  on  a  plain  white  paper,  also  an  ether  solution  of  a  volatile 
oil  found  on  side  shelf.  Watch  behavior  of  the  two  oils,  and 
report  differences,  if  any. 

Exp.  149.  Dissolve  a  little  butter  in  warm  alcohol,  examine 
with  the  microscope,  and  micropolariscope  the  crystals,  which 
separate  on  cooling. 

Note. —  If  possible  perforin  the  next  experiment  in  triplicate,  i.e.  carry  three  experiments  along 
at  the  same  time  using  for  "  fat "  the  Glyceryl  ester  of  the  three  most  common  fat  acids:  Olein 
(lard  oil  or  olive  oil),  Stearin  (beef  fat  or  tallow),  Palmatin  (bayberry  wax  or  tallow,  which  contains 
a  large  amount  of  free  palmitic  acid) . 

Exp.  150.  Saponification.  —  To  about  2  grams  of  solid  fat 
placed  in  a  narrow  beaker,  or  150  c.c.  Erlenmeyer  flask,  add  10 
or  15  c.c  of  alcoholic  solution  of  potassium  hydroxid.  Allow 
the  beaker  to  stand  on  the  water-bath  till  the  alcohol  is  entirely 
evaporated,  then  dissolve  the  resulting  soap  in  water;  filter,  if 
necessary,  to  obtain  a  clear  solution  and  make  the  following  tests: 

{a)  Add  to  a  portion  of  solution  a  saturated  solution  of 
sodium  chlorid.     What  takes  place  ? 

{h)  To  another  portion  add  a  few  cubic  centimeters  of  a  so- 
lution of  calcium  or  magnesium  chlorid.     Explain  the  results. 

(c)  Pour  the  remainder  slowly,  and  with  constant  stirring, 
into  warm  dilute  H2SO4,  and  heat  on  the  water-bath.  What  is 
the  result  ?  Write  the  equation.  Transfer  the  mixture  to  a  filter- 
paper  which  has  been  moistened  with  hot  water,  and  wash  with 
hot  water  till  all  H2SO4  is  removed.     Reserve  the  filtrates. 

Exp.  151.     Fatty  acids. 

(a)  Dissolve  a  portion  of  the  above  precipitates  (150  c)  by 
warming  with  strong  alcohol.     Test  the  reaction  of  the  solution. 


FATS  AND  OILS  269 

Examine  the  crystals,  which  separate  upon  standing,  with  micro- 
scope and  micropolariscope.     (Plate  VII,  Fig,  3,  page  296.) 

(&)  Add  to  a  portion  a  few  cubic  centimeters  of  a  strong 
NaaCOs  solution,  and  heat  till  the  fatty  acids  dissolve.  Cool. 
What  takes  place?     Explain  the  reaction.     Reserve  the  jelly. 

Exp.  152.  Neutralize  the  filtrates  of  146  c  and  evaporate 
almost  to  dryness  on  the  water-bath.  Extract  with  alcohol 
and  evaporate.  Note  the  taste.  Heat  another  portion  of  the 
residue  with  a  little  powdered  dry  KHSO4  in  a  dry  test-tube, 
and  note  the  odor,  which  is  due  to  acrolein,  CH2  =  CH-CH0. 
Fuse  some  borax  and  glycerin  on  a  platinum  loop:  green  color. 

Exp.  153.  Emulsification.  —  {a)  Put  i  to  2  c.c.  of  a  solution 
of  sodium  carbonate  (0.25%)  on  a  watch-glass,  and  place  in 
the  center  a  drop  of  rancid  oil.  The  oil-drop  soon  shows  a 
white  rim,  and  a  white  milky  opacity  extends  over  the  solution. 
Note  with  the  microscope  the  active  movements  in  the  vicinity 
of  the  fat-drop,  due  to  the  separation  of  minute  particles  of  oil 
(Gad's  experiment). 

(6)  Take  six  test-tubes  and  arrange  as  follows : 

1.  10  c.c.  of  a  0.2%  Na2C03  solution  -f  2  drops  of  neutral 

oil. 

2.  10  c.c.  of  a  0.2%  Na2C03  solution  +  2  drops  of  rancid 

oil. 

3.  10  c.c.  of  soap-jelly  (see  151  h),  warm,  -|-  2  drops  of 

neutral  oil. 

4.  10  c.c.  of  albumin  solution  +  2  drops  of  neutral  oil. 

5.  10  c.c.  of  gum-arabic  solution  +  2  drops  of  neutral  oil. 

6.  10  c.c.  of  water  -f  2  drops  of  neutral  oil. 

Shake  all  the  mixtures  thoroughly  and  note  the  results. 
What  conclusions  do  you  form  relative  to  the  influence  of  con- 
ditions upon  emulsification? 

(c)  Examine  a  drop  of  an  emulsion  under  the  microscope. 


CHAPTER  XXXII. 

PROTEINS. 

Protein  *  is  a  general  term  used  to  designate  the  nitrogenized 
bodies  which  constitute  the  greater  proportion  of  animal  tissue. 

While  meat  and  "protein"  are  usually  associated,  it  must 
not  be  forgotten  that  meat  is  not  the  exclusive  source  of  protein, 
for  we  usually  find  protein  in  vegetable  substances  and  often  to 
a  considerable  extent. 

UnHke  the  two  other  great  divisions  of  food  substances  (carbo- 
hydrates and  fats),  the  structure  of  the  protein  molecule  is  so 
complex  that  with  a  few  exceptions  of  the  simplest  kind  its 
representation  has  not  been  attempted. 

The  protein  molecule  contains  nitrogen  (often  as  the  amino 
group  NH2)  in  addition  to  the  C,  H,  and  0  of  the  carbohydrates 
and  fats.  It  frequently  contains  sulphur,  often  phosphorus, 
and  occasionally  the  metallic  elements,  particularly  iron. 

As  examples  of  the  complexity  of  protein  molecules,  the 
following  proposed  formulas  are  given  in  Hawk's  Physiologi- 
cal Chemistry. 

Serum  albumin,  C450H720N116S6O140. 

Oxyhaemoglobin,  C658Hii8iN207S2Fe02io. 

While  a  classification  of  proteins  according  to  their  chemical 
composition  is  at  present  practically  impossible,  the  following 
may  be  of  interest. 

After  Hofmeister,  Ergebnisse  der  Physiologic,  Jahrg.  I. 

*  The  term  Proteid  was  formerly  used  instead  of  Protein,  but  in  accordance 
with  the  recommendations  of  the  Committees  of  the  American  Physiological  and 
Biochemical  Societies,  it  has  been  abandoned.  The  classification  and  definitions 
herewith  given  are  taken  from  their  recommendation  as  printed  in  Science,  Vol. 
27,  No.  692,  page  554. 

270 


PROTEINS  271 

I.   Groups  or  the  Aliphatic  Series. 

A.  Group  containing  C,  N,  H. 

The  only  representative  known  is  the  guanidin  radical 
(CNH).NH2. 

B.  Groups  containing  C,  N,  H,  O. 

1.  Amino-acids. 

{a)  Monamino-acids. 

1.  Monobasic  monamino-acids,  CnH2n+iN02. 

C2  is  glycocoll. 

C3  is  alanin. 

C5  is  aminovalerianic  acid. 

Ceisleucin,  which  occurs  universally. 

2.  Dibasic  monamino-acids,  CnH2n-iN04. 

C4  is  asparaginic  acid. 
C5  is  glutaminic  acid. 

(&)  Diamino-acids  (all  monobasic  acids). 

C2  is  diaminoacetic  acid  (rare). 
Argynin  (guanidin-a-aminovalerianic  acid) .     Here  the 
diamino-acid  is  combined  with  the  guanidin  radical, 

NH2.NH.C.NH.CH2.(CH2)2.CH.NH2COOH. 

Lysin  (a-e-diaminocapronic  acid), 

NH2.CH2.(CH2)3.CH.NH2.COOH. 

2.  Amino-alcohols. 

Glucosamin,  C6Hn05(NH2),  a  hexose  into  which 
NH2  has  entered  the  carbohydrate  group  of  the 
protein  molecule. 

C.    Groups  containing  C,  N,  H,  O,  S. 

Cystein,aminothiolacticacid,CH2.SH.CH(NH2).COOH. 
Cystin,  the  sulphid  of  cystein,  C6H12S2N2O4. 
a-thiolactic  acid. 


272  PHYSIOLOGICAL   CHEMISTRY 

II.   Groups  of  the  Aromatic  Series. 

A.  Phenylalanin,  C6H5.CH2.CH(NH2).COOH. 

B.  Tyrosin,  C6H4.0H.CH2.CH(NH2).COOH. 

III. 

A.  Pyrrol  group. 

CH-CH-CH-CH.COOH 

I .   a-pyrrolidin  carbonic  acid,   I  I 

L— NH ' 

B.  Indol  group. 

1.  Indol,  see  page  250. 

2.  Skatol  (methyl  indol),  see  page  250. 

3.  Tryptophan  (indolaminopropionicacid),CiiHi2N202. 

4.  Skatosin,  C10H16N2O2. 

C.  Pyridin  group. 

Pyridin,  see  structural  formula  on  page  249. 

D.  Pyrimidin  group. 

Histidin:   structural  formula  probably 

NH CH 

I  II 

CH  =  C  -  N  -  CH2  -  CHNH2  -  COOH. 

Excepting  the  carbohydrate  group,  and  perhaps  the  pyridin 
and  pyrimidin  groups,  which  are  absent  in  a  few  special  in- 
stances, all  typical  proteins  contain  at  least  one  representative 
from  each  group. 

A  much  more  practical  classification,  based  in  part  upon  the 
properties  of  the  substance,  is  that  suggested  by  the  Joint  Com- 
mittees on  Protein  Nomenclature  (footnote,  page  270). 

"  Since  a  chemical  basis  for  the  nomenclature  of  the  proteins 
is  at  present  not  possible,  it  seems  important  to  recommend 
a  few  changes  in  the  names  and  definitions  of  generally  accepted 
groups,  even  though,  in  many  cases,  these  are  not  wholly 
satisfactory."     The  recommendations  are  as  follows: 


PROTEINS  273 

First.     The  word  proteid  should  be  abandoned. 

Second.  The  word  protein  should  designate  that  group  of 
substances  which  consists,  so  far  as  is  known  at  present,  essen- 
tially of  combinations  of  a-amino  acids  and  their  derivatives, 
e.g.,  cn-aminoacetic  acid  or  glycocoll;  a-amino  propionic  acid  or 
alanin;  phenyl-a-amino  propionic  acid  or  phenylalanin;  guan- 
idin-amino  valerianic  acid  or  arginin,  etc.,  and  are  therefore 
essentially  polypeptids. 

Third.  That  the  following  terms  be  used  to  designate  the 
various  groups  of  proteins : 

I.   Simple  Proteins. 

Protein  substances  which  yield  only  «-amino  acids  or  their 
derivatives  on  hydrolysis. 

Although  no  means  are  at  present  available  whereby  the 
chemical  individuality  of  any  protein  can  be  established,  a 
number  of  simple  proteins  have  been  isolated  from  animal  and 
vegetable  tissues  which  have  been  so  well  characterized  by  con- 
stancy of  ultimate  composition  and  uniformity  of  physical 
properties  that  they  may  be  treated  as  chemical  individuals 
until  further  knowledge  makes  it  possible  to  characterize  them 
more  definitely. 

The  various  groups  of  simple  proteins  may  be  designated  as 
follows : 

{a)  Albumins.  —  Simple  proteins  soluble  in  pure  water  and 
coagulable  by  heat;  e.g.,  ovalbumin,  serum  albumin,  lactalbumin, 
vegetable  albumins. 

(&)  Globulins.  — ■  Simple  proteins  insoluble  in  pure  water,  but 
soluble  in  neutral  solutions  of  salts  of  strong  bases  with  strong 
acids;*  e.g., f  serum  globuhn,  ovoglobulin,  edestin,  amandin,  and 
other  vegetable  globuHns. 

*  The  precipitation  limits  with  ammonium  sulphate  should  not  be  made  a 
basis  for  distinguishing  the  albumins  from  the  globulins. 

t  The  examples  of  the  various  proteins  are  those  given  by  Prof.  P.  B.  Hawk. 


274  PHYSIOLOGICAL   CHEMISTRY 

(c)  Glutelins.  —  Simple  proteins  insoluble  in  all  neutral 
solvents  but  readily  soluble  in  very  dilute  acids  and  alkalies;* 
e.g.,  glutenin. 

(J)  Alcohol-soluble  Proteins  (Prolamins).  —  Simple  proteins 
soluble  in  relatively  strong  alcohol  (70  to  80  per  cent),  but  in- 
soluble in  water,  absolute  alcohol,  and  other  neutral  solvents;! 
e.g.,  zein,  gliadin,  hordein,  and  bynin. 

(e)  Albuminoids.  —  Simple  proteins  which  possess  essentially 
the  same  chemical  structure  as  the  other  proteins,  but  are 
characterized  by  great  insolubility  in  all  neutral  solvents;  J  e.g., 
elastin,  collagen,  keratin. 

(/)  Histones.  —  Soluble  in  water  and  insoluble  in  very  dilute 
ammonia  and,  in  the  absence  of  ammonium  salts,  insoluble  even 
in  an  excess  of  ammonia;  yield  precipitates  with  solutions  of 
other  proteins  and  a  coagulum  on  heating  which  is  easily  soluble 
in  very  dilute  acids.  On  hydrolysis  they  yield  a  large  number 
of  amino  acids,  among  which  the  basic  ones  predominate;  e.g., 
globin,  thymus  histone,  scombrone. 

(g)  Protamins.  —  Simpler  polypeptids  than  the  proteins  in- 
cluded in  the  preceding  groups.  They  are  soluble  in  water,  un- 
coagulable  by  heat,  have  the  property  of  precipitating  aqueous 
solutions  of  other  proteins,  possess  strong  basic  properties  and 
form  stable  salts  with  strong  mineral  acids.  They  yield  com- 
paratively few  amino  acids,  among  which  the  basic  amino  acids 
greatly  predominate;  e.g.,  salmine,  sturine,  clupeine,  scombrine. 

*  Such  substances  occur  in  abundance  in  the  seeds  of  cereals  and  doubtless 
represent  a  well-defined  natural  group  of  simple  proteins. 

t  The  sub-classes  defined  {a,  h,  c,  d)  are  exemplified  by  proteins  obtained  from 
both  plants  and  animals.  The  use  of  appropriate  prefixes  will  suffice  to  indicate 
the  origin  of  the  compounds,  e.g.,  ovoglobulin,  myoalbumin,  etc. 

%  These  form  the  principal  organic  constituents  of  the  skeletal  structure  of 
animals  and  also  their  external  covering  and  its  appendages.  This  definition  does 
not  provide  for  gelatin,  which  is,  however,  an  artificial  derivative  of  collagen. 


PROTEINS  275 

II.   Conjugated  Proteins. 

Substances  which  contain  the  protein  molecule  united  to 
some  other  molecule  or  molecules  otherwise  than  as  a  salt. 

(a)  Nucleoproteins.  —  Compounds  of  one  or  more  protein 
molecules  with  nucleic  acid;  e.g.,  cystoglobuHn,  nucleohistone. 

(&)  Glycoproteins.  —  Compounds  of  the  protein  molecule 
with  a  substance  or  substances  containing  a  carbohydrate  group 
other  than  a  nucleic  acid;  e.g.,  mucins  and  mucoids  (osseomu- 
coid, tendomucoid,  ichthuHn,  hehcoprotein) . 

(c)  Phospho proteins.  — -  Compounds  of  the  protein  molecule 
with  some,  as  yet  undefined,  phosphorus- containing  substance 
other  than  a  nucleic  acid  or  lecithins;*  e.g.,  caseinogen,  vitellin. 

{d)  Hcemoglohins.  —  Compounds  of  the  protein  molecule  with 
hematin  or  some  similar  substance;  e.g.,  haemoglobin,  hsemo- 
cyanin. 

(e)  Lecitho proteins.  —  Compounds  of  the  protein  molecule 
with  lecithins  (lecithans,  phosphatids) ;  e.g.,  lecithans,  phos- 
phatids. 

III.   Derived  Proteins. 

I.  Primary  Protein  Derivatives. — Derivatives  of  the  pro- 
tein molecule  apparently  formed  through  hydrolytic  changes 
which  involve  only  slight  alterations  of  the  protein  molecule. 

(a)  Proteans.  — ■  Insoluble  products  which  apparently  result 
from  the  incipient  action  of  water,  very  dilute  acids  or  enzymes ; 
e.g.,  myosan,  edestan. 

{h)  Metaproteins.  —  Products  of  the  further  action  of  acids 
and  alkalies  whereby  the  molecule  is  so  far  altered  as  to  form 
products  soluble  in  very  weak  acids  and  alkalies,  but  insoluble 
in  neutral  fluids. 

*  The  accumulated  chemical  evidence  distinctly  points  to  the  propriety  of 
classifying  the  phosphoproteins  as  conjugated  compounds;  i.e.,  they  are  possibly 
esters  of  some  phosphoric  acid  or  acids  and  protein. 


276  PHYSIOLOGICAL   CHEMISTRY 

This  group  will  thus  include  the  familiar  "  acid  proteins  "  and 
"alkali  proteins,"  not  the  salts  of  proteins  with  acids;  e.g.,  acid 
metaproteins  (acid  albuminate),  alkali  metaprotein  (alkali 
albuminate) . 

(c)  Coagulated  Proteins.  —  Insoluble  products  which  result 
from  (i)  the  action  of  heat  on  their  solutions,  or  (2)  the  action 
of  alcohols  on  the  protein. 

2.  Secondary  Protein  Derivatives.*^  —  Products  of  the  further 
hydrolytic  cleavage  of  the  protein  molecule. 

{a)  Proteoses.  —  Soluble  in  water,  uncoagulated  by  heat,  and 
precipitated  by  saturating  their  solutions  with  ammonium  sul- 
phate or  zinc  sulphate;!  e.g.,  protoproteose,  deuteroproteose. 

(&)  Peptones.  —  Soluble  in  water,  uncoagulated  by  heat,  but 
not  precipitated  by  saturating  their  solutions  with  ammonium 
sulphate;!  e.g.,  antipeptone,  amphopeptone. 

(c)  Peptids.  —  Definitely  characterized  combinations  of  two 
or  more  amino  acids,  the  carboxyl  group  of  one  being  united 
with  the  amino  group  of  the  other,  with  the  elimination  of  a 
molecule  of  water;  §  e.g.,  dipeptids,  tripeptids,  tetrapeptids, 
pentapeptids. 

Laboratory  Exercise  LXIII. 

General  Protein  Reactions. 

Exp.  154.  Test  dried  egg-albumin  for  C,  H,  S,  and  N,  ac- 
cording to  the  methods  described  on  pages  182  and  183.  Test 
casein  for  phosphorus,  and  dried  blood  for  iron. 

*  The  term  secondary  hydrolytic  derivatives  is  used  because  the  formation  of  the 
primary  derivatives  usually  precedes  the  formation  of  these  secondary  derivatives. 

t  As  thus  defined,  this  term  does  not  strictly  cover  all  the  protein  derivatives 
commonly  called  proteoses;  e.g.,  heteroproteose  and  dysproteose. 

X  In  this  group  the  kyrins  may  be  included.  For  the  present  we  believe  that 
it  will  be  helpful  to  retain  this  term  as  defined,  reserving  the  expression  peptid 
for  the  simpler  compounds  of  definite  structure,  such  as  dipeptids,  etc. 

§  The  peptones  are  undoubtedly  peptids  or  mixtures  of  peptids,  the  latter  term 
being  at  present  used  to  designate  those  of  definite  structure. 


PROTEINS  277 

There  are  several  reactions  which  are  common  to  nearly  all 
proteins.  For  the  following  tests  use  a  solution  of  egg-albumin 
(1/50)  in  water,  as  a  general  type  of  a  protein. 

I.   Color  Reactions. 

Exp.  155.  Xanthoproteic  Test. — To  10  c.c.  of  the  albumin 
solution  add  one  third  as  much  concentrated  HNO3;  there  may 
or  may  not  be  a  white  precipitate  produced  (according  to  the 
nature  of  the  protein  and  the  concentration).  Boil;  the  pre- 
cipitate or  Hquid  turns  yellow.  When  the  solution  becomes 
cool  add  an  excess  of  NH4OH,  which  gives  an  orange  color. 
(This  color  constitutes  the  essential  part  of  the  test.) 

Exp.  156.  Milton's  Test.  — Add  a  few  drops  of  Millon's  re- 
agent *  to  a  part  of  the  albumin  solution.  A  precipitate,  which 
becomes  brick-red  upon  heating,  forms.  The  Hquid  is  colored 
red  in  the  presence  of  non-coagulable  protein  or  minute  traces 
of  albumin. 

Exp.  157.  Piotrowski's  Test. — ^  To  a  third  portion  add  2 
drops  of  a  very  dilute  solution  of  CUSO4,  and  then  5  to  10  c.c. 
of  a  40%  solution  of  NaOH.  The  solution  becomes  blue  or 
violet.  Proteoses  and  peptones  give  a  rose-red  color  (biuret 
reaction)  if  only  a  trace  of  copper  sulphate  is  used;  an  excess 
of  CUSO4  gives  a  reddish-violet  color,  somewhat  similar  to  that 
obtained  in  the  presence  of  other  proteins.  This  test  responds 
with  all  proteins. 

2.   General  Precipitants. 

Proteins  are  precipitated  from  solution  by  the  following  re- 
agents (peptones  are  exceptions  in  some  cases) : 

Exp.  158.  Acetic  Acid  and  Potassic  Ferrocyanid. — Make 
part  of  the  solution  to  be  tested  strongly  acid  with  acetic  acid, 

*  Mercuric  nitrate  in  nitric  acid.  For  the  preparation  of  this  and  other  reagents, 
see  Appendix. 


278  PHYSIOLOGICAL   CHEMISTRY 

and  add  a  few  drops  of  potassic  ferrocyanid  solution.  A  white 
flocculent  precipitate  is  formed  (not  with  peptones) . 

Exp.  159.  Alcohol.  — To  another  part  add  one  or  two  vol- 
umes of  alcohol. 

Exp.  160.  —  Tannic  Acid.  —  Make  the  solution  acid  with 
acetic  acid,  and  add  a  few  drops  of  tannic-acid  solution. 

Exp.  161.  Fotassio-mer curie  lodid. — Make  acid  another 
portion  with  HCl,  and  add  a  few  drops  of  the  reagent. 

Exp.  162.  Neutral  Salts.  —  Certain  neutral  salts  precipitate 
most  proteins.  (NH4)2S04  added  to  complete  saturation  to 
protein  solutions,  faintly  acid  with  acetic  acid,  precipitates  all 
proteins,  with  the  exception  of  peptones. 

Simple  Proteins. 
Albumins. 

The  albumins  are  conveniently  represented  by  egg-albumin 
and  serum-albumin.  They  are  soluble  in  water,  respond  to  the 
general  protein  reactions  (Exp.  155,  page  277,  etc.),  and  may  be 
completely  precipitated  by  saturation  of  the  solution  by  am- 
monium sulphate.     Albumin  is  coagulated  by  heat  (75°  to  80°  C). 

Egg-albumin  differs  from  serum-albumin  in  that  it  is  not 
absorbed  when  injected  into  the  circulation,  but  appears  un- 
changed in  the  urine.  Egg-albumin  is  readily  precipitated  from 
aqueous  solution  by  alcohol,  while  serum-albumin  is  precipi- 
tated only  with  difficulty.  Albumins  in  general  form,  with 
acids  or  with  alkalies,  derived  albumins  known  as  acid  or  alkali 
albumins  or  albuminates  (acid  or  alkaH  metaproteins) .  An  acid 
albumin  derived  from  myosin  is  known  as  syntonin.  It  differs 
but  sHghtly  from  other  acid  albumins.  The  acid  and  alkaU 
albumins  are  both  precipitated  by  neutrahzation,  but  neither  of 
them  are  coagulated  by  heat. 

If  the  hydrolysis  of  albumin  is  brought  about  by  HCl  at  the 
body   temperature,   it  causes   the  molecule   to   split  into   two 


PROTEINS  279 

proteins,  one  known  as  antialbuminate  and  the  other  as  hemi- 
albumose,  these  in  turn  becoming  respectively  antialbumid  and 
hemipeptone.  Sulphuric  acid  at  a  boiUng  temperature  produces 
a  similar  change,  except  that  the  hemipeptone  is  further  changed 
to  leucin  and  tyrosin.  Digestive  ferments,  pepsin,  and  trypsin 
produce  antialbumose,  hemiantipeptone,  and  hemialbumose, 
but  trypsin  alone  converts  the  hemipeptone  into  leucin  and 
tyrosin. 

Albumin  normally  occurs  in  all  the  body  fluids  except  in  the 
urine.  The  amount  in  milk  is  extremely  slight;  the  amount  in 
saHva  seems  to  vary  in  inverse  proportion  to  mucin.  Albumin 
occurring  in  urine  in  appreciable  quantity  is  always  abnormal, 
although  in  many  cases  it  has  no  serious  significance  unless 
persistently  present  in  more  than  the  slightest  possible  trace. 

Globulin  occurs  in  both  plants  and  animals,  and  crushed 
hemp  seed  may  be  used  as  a  convenient  source  for  laboratory 
experiment.  It  is  also  associated  with  albumin  in  blood-plasma, 
and  may  be  separated  from  it  by  half  saturation  with  ammonium 
sulphate,  which  precipitates  the  globulin  only,  but  it  is  not  to 
be  distinguished  by  the  ordinary  protein  tests  and  reactions. 
The  albumin  of  albuminous  urine  always  consists  of  a  mixture 
of  these  two  proteins,  globuHn  and  albumin,  not,  however,  al- 
ways in  the  same  proportion.  The  globulins  are  not  soluble  in 
distilled  water  as  the  albumins  are,  but  a  very  small  quantity  of 
neutral  salt,  such  as  sodium  chlorid,  will  serve  to  effect  the  solu- 
tion. Globulin  is  thrown  out  of  solution  by  action  of  carbon 
dioxid  as  a  white  flocculent  precipitate.  By  dialysis  the  in- 
organic salts  necessary  for  its  solution  will  be  removed  and  the 
protein  will  be  precipitated.  It  is  also  thrown  out  by  saturation 
of  sodium  chlorid  or  magnesium  sulphate.  Globulin  is  coagu- 
lated by  heat  at  practically  the  same  temperature  as  serum- 
albumin;  i.e.,  75°  C. 


28o  PHYSIOLOGICAL   CHEMISTRY 

Laboratory  Exercise  LXIV. 
Experiments  with  Albumin  and  Globulin. 

The  albumins  and  globulins  respond  to  all  the  general  re- 
actions of  Laboratory  Exercise  No.  63. 

Exp.  163.  A  specimen  of  solid  egg-albumin,  prepared  by 
evaporating  a  solution  to  dryness  at  40°  C,  is  provided.  Test 
its  solubiUty  in  water,  alcohol,  acetic  acid,  KOH  solution,  and 
concentrated  HCl.     Report  results. 

Perform  the  following  additional  experiments,  using  a  dilute 
(1/50)  solution  of  egg-albumin. 

Exp.  164.  Nitric-acid  Test.  —  Take  15  c.c.  of  the  solution  in 
a  wine-glass,  incHne  the  glass,  and  allow  5  c.c.  of  concentrated 
HNO3  to  run  slowly  down  the  side  to  form  an  under  layer. 
What  other  proteins  respond  to  this  test  ? 

Exp.  165.  Picric-acid  Test.  —  Take  a  portion  of  the  albumin 
solution  and  add  a  few  drops  of  a  solution  of  picric  acid  acidified 
with  citric  acid  (Esbach's  reagent).  What  other  proteins  re- 
spond to  this  test? 

Exp,  166.  Action  of  {NH^^SOi-  —  To  10  c.c.  of  the  albumin 
solution  in  a  test-tube  add  some  solid  (NH4)2S04,  shaking 
until  solution  is  thoroughly  saturated.  Allow  to  stand  a  little 
while,  shaking  occasionally,  then  filter,  saving  the  filtrate  to  test 
for  albumin  by  the  heat  test.  Report  result.  Test  the  solu- 
biHty  of  the  precipitate  on  the  filter-paper. 

Exp.  167.  Action  of  MgSOi. — Perform  an  experiment 
Eimilar  to  Exp.  166  using  solid  MgS04  instead  of  (NH4)2S04. 
With  what  results  ? 

Exp.  168.  Salts  of  the  Heavy  Metals.  —  Note  the  action  of 
the  following:  AgNOg,  HgCl2,  CUSO4,  Pb(C2H302)2.  Use  solu- 
tions of  the  salts  and  of  albumin. 

Why  is  white  of  egg  an  antidote  in  cases  of  metallic  poison- 
ing? 


PROTEINS  281 


Globulins. 


The  following  tests  serve  to  distinguish  the  globulins  from 
other  proteins. 

The  tests  may  be  made  upon  blood  serum,  or  upon  a  globuHn 
(edestin)  which  may  be  separated  from  hemp  seed  according  to 
the  following  experiment: 

Extract  about  i  ounce  of  crushed  hemp  seed  with  water 
containing  about  5%  sodium  chlorid.  This  extraction  should 
take  from  one-half  hour  to  one  hour  at  a  temperature  of  about 
60°  C.  Filter  while  hot.  Upon  cooling,  a  portion  of  the  globu- 
lin (edestin)  will  probably  separate  out.  Use  the  clear  separated 
fluid  for  the  general  protein  reactions  and  precipitates.  Boil 
the  cloudy  portion  until  the  precipitated  globulin  has  dissolved.. 
Then  set  aside  for  24  hours  that  the  edestin  may  crystallize 
slowly,  when  hexagonal  plates  should  be  obtained.  Examine 
by  the  microscope.     (See  Plate  VII,  Fig.  i,  page  296.) 

Exp.  169,  Action  of  CO2.  —  To  5  c.c.  of  blood  serum  add 
45  c.c.  of  ice-cold  water.  Place  the  mixture  in  a  large  test-tube 
or  cylinder,  surround  it  with  ice-water,  and  pass  through  it  a 
stream  of  CO2.  A  flocculent  precipitate  (paraglobulin)  *  will  be 
formed. 

Exp.  170.  Precipitation  by  Dialysis.  —  Into  a  parchment 
dialyzing-tube,  previously  soaked  in  distilled  water,  pour  20  c.c. 
of  serum,  swing  the  tube,  with  its  contents,  into  a  large  vessel 
of  distilled  water,  which  is  to  be  changed  at  intervals.  Let 
stand  twenty-four  hours,  then  examine  the  serum  in  the  dialyz- 
ing-tube; it  will  contain  a  flocculent  precipitate  of  paraglobu- 
Un.     Give  explanation  of  cause  of  precipitation. 

Exp.  171.  Pour  a  solution  of  globulin,  drop  by  drop,  into  a 
large  volume  of  distilled  water  (in  a  beaker).  What  takes 
place  ?     Explain. 

*  Paraglobulin  is  a  name  applied  to  the  globulin  separated  from  blood  serum.. 


-282  PHYSIOLOGICAL   CHEMISTRY 

Exp.  172.  Precipitation  by  Magnesium  Sulphate.  —  Saturate 
about  5  c.c.  of  globulin  solution  with  solid  magnesium  sulphate. 
A  heavy  precipitate  will  be  formed.  Compare  this  with  the 
action  of  the  same  salt  on  the  egg-albumin  solution.  Paraglo- 
buHn  is  so  completely  precipitated  by  this  salt  that  the  method 
is  used  for  its  quantitative  estimation. 

The  glutelins  and  prolamins  thus  far  studied  have  been 
mostly  obtained  from  vegetable  sources. 

Glutenin  constitutes  about  one-half  of  wheat  gluten,  and 
the  prolamins  mentioned  on  page  274;  Zein  is  obtained  from 
maize  — •  Hordein  from  barley,  GHadin  from  wheat  or  rye  and 
Bynin  from  malt. 

Albuminoids. 

Albuminoids  are  the  simple  protiens  characterized  by  pro- 
nounced insolubility  in  all  neutral  saHvas,  and  the  common  exam- 
ples are  Keratin,  from  nails  and  hoofs,  etc. ;  Collagen,  from  bone 
and  connective  tissue;  and  Elastin,  from  tendons  and  ligaments. 

The  differences  in  these  substances  are  sHght,  the  keratin 
being  less  soluble  and  less  easily  acted  upon  by  digestive  ferments 
than  either  of  the  other  two.  Keratin  also  contains  more  sul- 
phur. It  is  the  principal  constituent  of  horn,  nails,  hair, 
feathers,  egg  membrane,  and  some  shells,  such  as  turtle  and 
tortoise.  The  sulphur  content  of  these  various  sources  differs 
considerably,  ranging  from  about  5%  in  hair,  about  3%  in  nail 
and  horn,  to  1.4%  in  egg  membrane. 

The  keratins  are  characterized  by  the  fact  that  the  sulphur 
which  they  contain  is  loosely  combined;  i.e.,  easily  separated  by 
the  formation  of  hydrogen  sulphide  and  other  sulphur  com- 
pounds as  proved  by  experiment  No.  174.  The  keratins  are 
insoluble  in  dilute  acids  and  unaffected  by  any  of  the  diges- 
tive ferments;  they  do,  however,  dissolve  in  the  caustic  alkali 
solutions,  and  may  be  used  as  the  source  of  leucin,  tyrosin, 
cystin,  and  other  well-known  products  of  protein  digestion. 


PROTEINS  283 

Collagen,  upon  hydrolization  with  boiling  water,  produces 
gelatin,  which  is  a  characteristic  property  of  this  class  of  pro- 
teins. It  may  be  dissolved  by  both  the  gastric  and  pancreatic 
juices,  especially  if  previously  treated  with  warm  acidulated 
water. 

Elastin  contains  the  least  sulphur  of  either  of  the  three  sub- 
stances which  we  have  considered.  It  may  be  obtained  from 
the  ligamentum  nuchae  of  an  ox  by  chopping  the  Hgament 
finely  and  extracting  for  two  or  three  days  with  half  saturated 
solution  of  calcium  hydroxid.  Like  collagen  it  is  dissolved  upon 
prolonged  treatment  with  proteolytic  ferments. 

Bone. 

If  all  organic  matter  is  burned  off  from  bone,  there  remains 
the  bone-earth,  so  called,  made  up  of  the  phosphates  and  car- 
bonates of  Hme  and  magnesia,  with  shght  amounts  of  chlorin, 
fluorin,  and  of  sulphates,  the  proportion  being  practically  the 
same  as  given  for  dentine,  under  Teeth,  on  page  178.  Because 
in  some  diseases,  in  which  the  bones  are  softened  or  decalcified 
(as  osteomalacia),  the  relation  of  the  CaO  and  P2O5  remains 
unchanged,  it  has  been  claimed  that  these  substances  exist  in 
the  bone  in  the  form  of  a  definite  phosphate-carbonate  contain- 
ing three  molecules  of  the  tribasic  phosphate  to  one  of  carbon- 
ate: 3  Ca3(P04)2-CaC03. 

If,  by  treatment  with  dilute  hydrochloric  acid,  the  min- 
eral constituents  are  entirely  dissolved  out  of  bone,  there  re- 
mains a  substance  from  which  glue  (gelatin)  is  derived,  of 
similar  composition  to  collagen,  from  connective  tissue,  and 
known  as  ossein.  Neither  of  these  (ossein  or  collagen)  is  sol- 
uble in  water  or  in  dilute  acids. 

Gelatin  is  made  by  hydrolysis  of  ossein  or  collagen  brought 
about  by  prolonged  boihng  with  dilute  mineral  acids.  Gelatin, 
if  first  treated  with  cold  water  till  soft,  may  be  dissolved  in  hot 


284  PHYSIOLOGICAL  CHEMISTRY 

water.  The  solution  is  precipitated  by  mercuric  chlorid,  alcohol, 
tannic,  and  picric  acids.  It  responds  but  feebly  to  the  general 
protein  reactions,  but,  by  digestion  with  either  pepsin  or  trypsin, 
compounds  are  obtained  analogous  to  those  resulting  from 
similar  protein  digestion. 

Laboeatory  Exercise  LXV. 
Experiments  with  Keratin  and  Gelatin, 

Keratins  are  characterized  by  their  insolubility,  and  by  their 
high  content  of  loosely  combined  sulphur. 

Exp.  173.  Test  solubility  of  keratin  (nail  or  horn)  in  water, 
acids,  alkahes,  gastric  and  pancreatic  juices. 

Exp.  174.  Warm  a  bit  of  keratin  with  5  c.c.  strong  NaOH 
solution  for  a  few  minutes,  and  add  a  few  drops  of  a  lead  acetate 
solution.     What  is  the  result  ? 

Exp.  175.  Gelatin.  —  Take  about  10  grams  of  bone,  prefer- 
ably small  pieces  of  the  shaft  of  a  long  bone,  clean  carefully, 
and  allow  to  stand  for  a  few  days  in  60  c.c.  of  dilute  HCl  (1/20). 
The  dilute  acid  dissolves  the  inorganic  portion  of  the  bone, 
leaving  the  collagen.  Note  the  effervescence  due  to  the  pres- 
ence of  carbonates.  The  acid  solution  is  poured  off  and  kept 
for  further  investigation.  The  remains  of  the  bone  are  allowed 
to  stand  over  night  in  a  dilute  solution  (i/io)  of  NaaCOa,  and 
then  boiled  in  100  c.c.  of  water  for  an  hour  or  two.  The  col- 
lagen undergoes  hydration  and  is  converted  into  gelatin,  which 
dissolves.  A  core  of  bone  untouched  by  the  acid  usually  re- 
mains. Evaporate  the  solution  to  25  c.c.  bulk  and  allow  to 
cool.  A  firm  jelly  is  formed  if  the  solution  is  sufficiently  con- 
centrated. If  the  solution  gelatinizes,  add  an  equal  bulk  of 
water  and  heat  anew.  With  the  solution  perform  the  following 
experiments.  (If  too  little  gelatin  is  obtained  for  all  the  tests,  a 
solution  will  be  provided.) 

Gelatin  may  also  be  prepared  from  tendons  which  consist 


PROTEINS  285 

almost  wholly  of  white  fibers.  Collagen  is  the  substance  of 
which  white  fibers  are  made  up. 

Exp.  176.  With  a  solution  of  gelatin  make  the  usual  tests 
for  protein. 

Exp.  177.  Precipitate  gelatin  from  dilute  solution  with  the 
following  reagents: 

{a)  Tannic  acid. 

{h)  Alcohol. 

(c)  Acetic  acid  and  potassium  ferrocyanid. 

{d)  Mercuric  chlorid. 

{e)  Picric  acid. 

Conjugated  Proteins. 

These  are  substances  which  contain  the  protein  molecule 
united  to  some  other  molecule  or  molecules  otherwise  than  as  a 
salt.  The  conjugated  proteins  which  we  shall  study  are  mucin, 
a  type  of  glyco-protein,  yielding  upon  decomposition  a  sub- 
stance containing  a  carbohydrate  group;  caseinogen  (from  milk), 
a  phosphorus  containing  substance;  and  hemoglobin  (from 
blood). 

The  glyco-protein.  Mucin,  a  selected  type  of  this  class  of 
protein  substance,  occurs  in  various  forms  in  saliva,  in  urine,  bile, 
and  other  body  fluids.  The  mucin  substances  are  differentiated 
from  the  true  mucins,  according  to  Hammarsten,  by  the  fact  that 
the  latter  form  mucilaginous  or  ropy  solutions  by  the  aid  of  a 
trace  of  alkali,  from  which  they  are  precipitated  by  acetic  acid. 
The  precipitate  is  insoluble  in  excess  of  acid,  or  soluble  only 
with  great  difficulty. 

True  mucins  have  been  separated  and  examined  from  the 
secretion  of  the  submaxillary  glands,  from  snails,  from  mucous 
membranes  of  the  air  passages,  from  synovial  fluid,  and  from  the 
navel  cord. 

Mucin  is  quite  readily  converted  to  metaprotein  by  boiling 
with  dilute  acid,  and,  by  action  of  strong  acid,  will  yield  a 


286  PHYSIOLOGICAL  CHEMISTRY 

number  of  the  simpler  amino  acids.  Mucin  itself  is  acid  in  re- 
action, but  there  is  no  evidence  that  it  has  power  to  form  salts. 

The  mucins  are  insoluble  in  pure  water,  but  dissolve  upon 
the  addition  of  traces  of  alkali.  The  solution  thus  obtained  will 
give  the  usual  color  reactions  for  the  proteins. 

The  action  of  mucin  as  a  factor  in  dental  caries,  formation  of 
gelatinous  plaques,  etc.,  will  be  discussed  under  Saliva. 

Caseinogen,  the  second  conjugated  protein  which  we  shall 
consider,  is  the  principal  nitrogenous  constituent  of  milk  and 
will  be  studied  as  such. 

Milk. 

Milk  is  the  characteristic  secretion  of  mammals  and  con- 
tains the  three  great  classes  of  food  material,  viz. :  the  proteins, 
carbohydrates  and  fats.  The  fat  is  held  as  a  permanent  emul- 
sion in  so-called  milk  plasma. 

The  plasma  consists  of  water  holding  in  solution  caseinogen, 
albumin  with  a  trace  of  globulin,  milk  sugar  (lactose)  and  mineral 
salts. 

Specific  Gravity.  —  Milk  contains  two  different  sorts  of  sub- 
stances influencing  the  gravity;  first,  the  fat  being  lighter  than 
the  water  tends  to  decrease  the  gravity;  second,  the  solids  not 
fat  which  are  heavier  than  water  tend  to  increase  the  gravity  of 
the  milk.  Consequently,  it  may  happen  that  a  very  poor  milk 
and  a  very  rich  milk  will  have  the  same  specific  gravity;  e.g.,  the 
normal  gravity  of  whole  milk  is  about  1.031,  while  the  gravity 
of  skim  milk  will  be  about  i  .035  or  i  .036,  and  that  in  which  cream 
occurs  in  large  amount  may  be  as  low  as  1.015  or  1.020.  It  can 
be  easily  seen  that  starting  with  whole  milk,  the  addition  of 
cream  or  the  addition  of  water  will  both  alike  reduce  the  gravity. 
Hence,  taken  alone,  the  gravity  tells  little  or  nothing  as  regards 
the  quahty  of  milk;  but,  if  the  gravity  is  taken  together  with 
the  fat  content,  the  two  factors  give  oftentimes  sufficient  infor- 
mation. 


PROTEINS  287 

The  relation  between  the  gravity  of  the  fat  and  the  total 
soHds  is  approximately  constant,  and  the  following  formula 
will  give  the  amount  of  total  solids  usually  within  o.io  or  0.15 
of  1%. 

Total  soUds  =  ?^t^^  +  ^Si^  +  0.46. 


Reaction.  —  The  reaction  of  cow's  milk,  when  perfectly 
fresh,  is  amphoteric  to  litmus;  i.e.,  it  will  both  redden  blue  litmus 
paper  and  turn  red  litmus  blue  at  the  same  time.  This  double 
reaction  is  due  to  the  presence  of  various  salts,  probably  the 
acid  and  alkaline  phosphates. 

Cow's  milk  is  acid  to  phenolphthalein,  and  this  acidity 
naturally  increases  by  the  multiplication  of  various  acid-forming 
bacteria,  which  produce  lactic  acid  by  hydrolysis  of  the  milk 
sugar.  When  the  acid  strength  has  increased  sufficiently,  the 
caseinogen  is  decomposed,  and  casein  is  produced  and  pre- 
cipitated. 

This  casein  constitutes  the  curd,  and  the  process  is  the 
ordinary  souring  of  milk. 

Lactic  acid  is  not  the  only  acid  produced  in  the  spontaneous 
fermentation  of  milk,  as  traces  of  formic,  acetic,  butyric  and 
succinic  acids  have  been  demonstrated  by  different  investiga- 
tors. 

The  degree  of  acidity  of  milk  is  conveniently  determined  as 
suggested  by  W.  Thorner  (Chem.  Zeit.,  1891,  page  1108,  abst. 
analyst  XVI,  200),  10  c.c.  of  milk  with  an  equal  volume  of  water 
and  a  few  drops  of  phenolphthalein  as  indicator  are  titrated  with 
N/io  alkaH  and  every  tenth  of  a  degree  of  alkali  used  is  con- 
sidered as  representing  one  "  degree  "  of  acidity. 

By  experimenting  on  samples  kept  under  various  con- 
ditions, Thorner  found  that  milk  coagulates  on  boihng  when 
the  acidity  reaches  23°.  Adopting  20°  as  the  permissible  hmit 
of  acidity,  he  proposes  the  following  test:  10  c.c.  of  milk,  20  c.c. 


288  PHYSIOLOGICAL   CHEMISTRY 

of  water,  a  few  drops  of  indicator  and  2  c.c.  of  decinormal 
alkali  are  thoroughly  mixed;  if  any  red  color,  however  weak, 
results,  the  milk  will  not  coagulate  upon  boiling.* 

This  method  is  given  partly  for  its  own  sake  and  partly  be- 
cause exactly  the  same  method  is  used  by  Dr.  Eugene  S.  Talbot 
of  Chicago  and  many  others  for  the  determination  of  acidity  of 
urine.  By  slight  modification  it  may  be  used  for  saliva.  The 
record  of  sHght  amounts  of  acidity  made  in  degrees  in  this  way 
has  several  practical  points  in  its  favor. 

Casein  is  the  principal  protein  found  in  milk.  It  exists  in 
combination  with  calcium  salts  as  caseinogen.  This  combina- 
tion is  broken  up  and  the  casein  precipitated  by  the  action  of 
rennin  and  other  enzymes,  by  acids,  and  by  certain  inorganic 
salts. 

Casein  is  classified  as  a  pseudo-nucleo-albumin.  The  nucleo- 
proteins,  so  named  because  true  nuclein  may  be  obtained  from 
them,  are  constituents  of  the  cell  nuclei,  and  differ  in  composi- 
tion from  ordinary  proteins  by  containing  from  0.5  to  1.6%  of 
phosphorus.  Casein  from  cow's  milk  contains,  according  to 
Hammarsten,  0.85%  of  phosphorus.  It  has  been  classified  as 
a  pseudo-imcleo-aXhmmn  because,  upon  digestion  with  pepsin, 
pseudo-nuclein  rather  than  true  nuclein  is  obtained. 

Casein  is  practically  insoluble  in  water,  but  dissolves  readily 
in  dilute  alkaHne  solutions.  Its  precipitation  as  curd  is  de- 
pendent upon  the  presence  of  calcium  salts. 

Lactalbumin  is  the  only  other  protein  substance  worthy  of 
note  in  milk.  This  may  be  found  in  the  filtrate  after  separat- 
ing the  casein.  The  total  proteins  contained  in  human  milk 
average  from  1.5  to  2.5  per  cent,  while  in  cow's  milk  the  proteins 
are  3.0  to  4.5  per  cent.  This  difference,  together  with  the  vari- 
ation of  reaction  and  sugar-content,  makes  it  necessary  to 
*' modify"  cow's  milk  when  it  is  used  as  an  infant  food. 

The  modification  usually  consists  in  the  addition  of  Hme- 

*  From  Allen's  Commercial  Organic  Analysis,  Vol.  4. 


PROTEINS 


289 


water  (to  change  the  reaction) ,  of  water  (to  reduce  percentage  of 
proteins),  and  of  cream  and  milk-sugar  (to  increase  fat  and 
lactose) . 

The  following  table  shows  comparative  composition: 


Reaction. 

Total 
Solids. 

Proteins. 

Sugar. 

Fat. 

Ash. 

Human  milk .  . 
Cow's  milk.  .  . 

Alkaline 
Acid 

13.00% 
14.00% 

2.70% 
4.15% 

6.10% 
4.90% 

4.00% 
4.25% 

0.20% 
0.70% 

Fat.  —  The  fat  of  milk  exists  as  microscopic  globules  appar- 
ently inclosed  in  a  protein-like  membrane  separating  substance, 
the  presence  af  which  seems  a  necessary  theory  to  account  for 
the  behavior  of  milk  fat  toward  various  solvents  such  as  ether. 
The  milk  fat  or  butter  fat  consists  largely  of  olein  and  palmitin 
with  a  slight  amount  of  butyrin  and  traces  of  several  other  fatty 
acids. 

Milk,  as  has  already  been  stated,  undergoes  lactic  acid 
fermentation  readily  and  this  may  be  induced  by  a  considerable 
number  of  microorganisms.  It  is 
not,  however,  Hable  to  alcoholic 
fermentation  except  under  peculiar 
circumstances.  Alcoholic  fermen- 
tation may  be  induced  by  certain 
ferments,  such  as  the  Kephir  grain 
used  quite  largely  in  the  East,  the 
product  being  known  as  Kumiss 
or  milk  wine.  Kumiss  originally 
was  produced  from  mare's  milk, 
but  the  name  has  also  been  applied 
to  any  milk  which  has  undergone  alcoholic  fermentation. 

Colostrum  is  a  pecuHar  substance  occurring  at  the  very 
earHest  stages  of  lactation.  Its  specific  gravity  is  considerably 
higher  than  that  of  milk,  being  1.040  to  1.060.     It  contains 


Milk  and  Colostrum. 


290  PHYSIOLOGICAL  CHEMISTRY 

much  more  protein  substance  and  is  characterized  by  the  pres- 
ence of  granular  corpuscles  known  as  colostrum  corpuscles. 
(Fig.  18,  on  page  289.) 

Laboratory  Exercise  LXVI. 

Experiments  with  Mucin  and  Milk. 

Exp.  178.  Examine  microscopically  whole  milkj  skim-milk, 
and  cream.  Note  the  relative  amounts  of  fat  in  the  three 
varieties. 

Exp.  179.  Shake  a  Httle  cream  with  chloroform  in  a  test- 
tube;  separate  the  chloroform,  evaporate,  and  melt  the  fat 
residue  obtained;  allow  it  to  cool  slowly,  when  fat  crystals  will 
be  obtained,  which  may  be  examined  under  the  microscope  and 
micropolariscope. 

Exp.  180.  With  a  lactometer  take  the  specific  gravity  of 
whole  milk  and  skim-milk  and  explain  the  difference  in  results. 

Exp.  181.     Test  the  reaction  of  mjlk  with  htmus. 

Exp.  182.  Dilute  some  milk  with  six  or  seven  times  its 
volume  of  water,  and  add  acetic  acid  drop  by  drop  till  the 
casein  is  precipitated.  Filter  and  reserve  the  precipitate.  Test 
the  filtrate  for  proteins,  if  any  remain;  determine  if  possible 
their  character. 

Exp.  183.  Test  another  portion  of  the  filtrate  for  carbohy- 
drates, determining  the  variety  present. 

Exp.  184.  To  50  c.c.  of  milk  add  a  few  drops  of  rennin 
solution;  keep  at  a  temperature  of  40°  C.  for  a  few  minutes, 
and  explain  results. 

Exp.  185.  Take  a  portion  of  the  precipitated  casein  from 
Exp.  182,  digest  at  40°  C.  with  pepsin  HCl  for  twenty  minutes 
or  hah  an  hour.  While  digesting,  test  other  portions  of  casein, 
for  solubility  in  water,  in  dilute  acid  and  dilute  alkali.  Test 
also  a  portion  for  phosphorus  by  boiling  in  a  test-tube  with 
dilute  nitric  acid,  cooHng  to  at  least  50°  C,  and  adding  ammo- 
nium molybdate  solution. 


PROTEINS  291 

Exp.  186.  To  a  little  skim-milk  contained  in  a  test-tube  add 
a  saturated  solution  of  ammonium  sulphate. 

Exp.  187.  To  a  solution  of  mucin*  found  on  the  side  shelf 
add  acetic  acid  till  precipitation  takes  place.  Settle,  filter, 
wash,  and  test  solubihty  in  water,  dilute  alkah  solution  and 
5%  HCl. 

Exp.  188.     Make  color-tests  for  proteins. 

Exp.  189.  Boil  a  little  mucin  solution  with  dilute  HCl  for 
several  minutes.     Cool,  neutraHze,  and  test  for  sugar. 

Derived  Proteins. 

Meta-proteins  —  Acid  Meta-protein.  —  The  digestive  action 
of  the  gastric  juice  on  protein  substances  is  the  formation  of  an 
acid  meta-protein,  formerly  called  acid  albuminate.  The  meta- 
proteins  are  characterized  by  the  fact  that  they  are  precipitated 
on  neutralization  and  are  not  coagulated  by  heat.  They  may 
also  be  precipitated  by  saturation  with  common  salt. 

The  Alkali  Meta-protein  or  alkali  albuminate  is  the  stronger 
of  these  two  classes  of  compounds  when  considered  from  a  chem- 
ical standpoint;  that  is,  the  reactions  are  more  marked,  and  some 
compounds  will  be  formed  with  the  alkah  albuminate  which  are 
not  produced  when  the  acid  albuminate  is  treated  in  a  similar 
way.  The  acid  meta-protein  from  the  digestion  of  meat  is  known 
as  syntonin. 

The  Proteoses  (albumoses)  may  be  considered  as  the  next 
well-defined  protein  product  of  protein  digestion  following  the 
albuminate.  That  is,  leaving  out  the  many  intermediate  prod- 
ucts between  which  sharp  lines  of  demarkation  cannot  be 
drawn,  the  decomposition  of  albumin  brought  about  by  enzymes 
or  digestive  ferments  gives,  first,  acid  albumin;  second,  albumose; 
and  third,  peptone.  Albumose  may  be  taken  as  a  type  of  this 
second  class  of  digestive  products.  Other  proteoses,  such  as 
globulose,  etc.,  are  the  substances  derived  from  other  proteins 

*  For  preparation  of  mucin  solution  from  navel  cord,  see  Appendix. 


292  PHYSIOLOGICAL  CHEMISTRY 

at  a  corresponding  point  of  decomposition  or  peptic  digestion. 
Albumose  may  be  coagulated  by  heat  at  a  temperature  ranging 
upwards  from  56°  C,  but,  unlike  albumin,  as  the  temperature 
approaches  the  boiling-point  the  albumose  goes  again  into  solu- 
tion, and  at  a  boiling  temperature  may  be  separated  from  albumin 
by  filtration.  As  the  filtrate  cools,  albumose  will  again  precipi- 
tate. The  albumose  is  also  precipitated  by  nitric  acid,  by  ferro- 
cyanid  of  potassium  and  acetic  acid  (the  precipitate  in  both  cases 
being  dissolved  by  heat),  and  the  other  general  protein  precipi- 
tates. The  biuret  test  gives  a  distinctive  color  with  proteoses 
and  peptones,  it  being  a  marked  reddish  shade  rather  than  the 
violet  or  blue  obtained  with  other  proteins. 

Peptones  are  the  final  products  of  peptic  digestion  of  the 
proteins.  They  are  soluble  substances  which  give  the  biuret 
test  similarly  to  the  proteoses,  but  are  not  precipitated  by  heat, 
by  nitric  acid,  by  potassium  ferrocyanid  and  acetic  acid,  nor 
by  saturation  with  ammonium  sulphate. 

Peptids.  —  The  peptids  are  the  simpler  forms  of  the  pep- 
tones, many  of  them  being  complex  amino  acids.  Upon  decom- 
position or  hydrolytic  splitting  of  peptid,  the  simpler  amino  acid, 
which  is  without  the  protein  characteristics,  results. 

Laboratory  Exercise  LXVII. 
Experiments  with  Protein  Derivatives. 

Preparation  of  Metaprotein.  To  a  solution  of  egg-albumin 
add  a  few  drops  of  a  0.5%  solution  of  NaOH,  and  warm  gently 
for  a  few  minutes.  With  the  solution  thus  obtained  perform 
the  following  tests : 

Exp.  190.  {a)  Effect  of  Heating.  —  Boil  some  of  the  solution 
and  report  result. 

Exp.  191.  (b)  Effect  of  Neutralizing. — Add  a  drop  of 
litmus  solution,  and  cautiously  neutralize. 


PROTEINS  293 

Acid  Metaprotein. 

Exp.  192.  Add  a  small  quantity  of  a  0.2%  HCl  solution  to  a 
solution  of  egg-albumin,  and  warm  at  40°  C.  for  one  half  to  one 
hour.  Or  cover  with  an  excess  of  0.2%  HCl  some  meat  cut 
into  fine  pieces,  and  expose  for  a  while  to  a  temperature  of 
40°  C.  Filter.  With  either  of  the  solutions  thus  obtained 
make  same  tests  as  on  alkali  metaprotein,  and  compare  results. 
How  distinguish  between  them? 

Albumoses  (Hemialbumose) .  — ■  This  name  includes  four 
closely  alHed  forms  of  albumose,  namely:  (i)  Protoalbumose; 
(2)  Deuteroalbumose;  (3)  Heteroalbumose;  (4)  Dysalbumose, 
an  insoluble  modification  of  heteroalbumose.  Commercial 
peptone,  which  is  substantially  a  mixture  of  albumoses  and  pep- 
tones, will  be  given  out  for  use. 

Exp.  193.  Make  a  solution  of  the  peptone  in  water,  filter 
if  necessary,  and  saturate  with  solid  (NH4)2S04.  Filter.  The 
precipitate  contains  the  albumoses,  the  filtrate  the  peptones. 
Reserve  the  filtrate  for  subsequent  tests  for  peptone.  Wash  the 
precipitate  with  a  saturated  solution  of  ammonium  sulphate; 
dissolve  in  water,  and,  with  the  solution  obtained,  perform  the 
following  tests,  noting  especially  the  tendency  of  albumose  pre- 
cipitates to  dissolve  upon  the  application  of  heat  and  to  reappear 
upon  cooling. 

Using  this  solution  of  albumose,  repeat  Exps.  155,  156,  157, 
164,  165.  If  no  precipitate> forms  with  HNO3  in  Exp.  164,  add 
a  drop  or  two  of  a  saturated  solution  of  common  salt.  (Deutero- 
albumose gives  this  reaction  only  in  the  presence  of  HCl.) 

Exp.  194.  Saturate  some  of  the  solution  with  (NH4)2S04. 
Report  the  result. 

Exp.  195.  To  some  of  the  solution  add  2  or  3  drops  of  acetic 
acid  and  then  a  saturated  solution  of  NaCl.  A  precipitate 
forms,  which  dissolves  on  heating,  and  reappears  on  cooling. 

Exp.  196.     Using  the  peptone  solution  prepared  in   manner 


294  PHYSIOLOGICAL   CHEMISTRY 

above  described  from  commercial  peptone,  repeat  the  experi- 
ments indicated  in  Exp.  193. 

Exp.  197.  Efect  of  heating.  —  Boil  some  of  the  peptone  solu- 
tion.    Report  the  result. 

Exp.  198.  Power  of  Dialyzing.  —  Dialyze  some  of  the  pep- 
tone solution.  Use  10  c.c.  of  the  peptone  solution,  and  in  the 
outside  vessel  about  100  c.c.  of  water,  which  in  this  case  is  not 
to  be  changed.  After  twenty-four  hours  test  the  outside  water 
for  peptone,  employing  the  biuret  test. 

Exp.  199.  Action  of  Ammonium  Sulphate.  —  Saturate  some 
of  the  peptone  solution  with  soHd  (NH4)2S04.  Report  the 
result. 

A  number  of  unknown  solutions  will  be  given  out  to  be 
tested  for  carbohydrates  and  proteins.  A  report  of  the  results, 
together  with  the  methods  employed,  is  to  be  made. 


BLOOD   AND   MUSCLE. 

Blood. 

The  blood,  carrying  oxygen  and  other  forms  of  nutrition  to 
all  parts  of  the  body,  and  returning  carbon  monoxid  and  the 
waste  products  of  cellular  activity,  is  an  exceedingly  complex 
substance.  The  composition  of  the  blood  itself,  however,  may 
be  grossly  described  as  a  fluid  (plasma)  carrying  in  suspension 
the  cellular  constituents,  red  and  white  corpuscles.  The  plasma 
contains  solid  matter  to  the  extent  of  about  8.9%.  This  is 
largely  protein,  consisting  of  serum  globulin,  serum  albumin, 
a  sHght  amount  of  nucleoprotein,  and  fibrinogen;  also  a  fibrin 
ferment,  thrombase  or  thrombin,  by  the  action  of  which  the 
fibrin  is  separated  as  a  "clot"  which  mechanically  carries  down 
the  corpuscles.  As  the  clot  contracts,  the  "serum"  separates 
as  a  clear,  amber-colored  liquid,  consisting  of  serum  globuHn 
(paraglobuHn),  serum  albumin,  and  the  fibrin  ferment. 


BLOOD  AND   MUSCLE  295 

Fibrin.  —  The  fibrin  may  be  obtained  free  from  corpuscles 
by  whipping  fresh  blood.  Under  this  treatment  the  fibrin 
separates  as  shreds,  while  the  remaining  fluid  constitutes 
"defibrinated  blood."  The  presence  of  lime-salts  is  essential 
to  the  coagulation  of  the  blood,  i.e.,  the  decomposition  of  fibrin- 
ogen and  separation  of  fibrin,  in  much  the  same  way  as  in  the  de- 
composition of  caseinogen  and  precipitation  of  casein  from  milk. 

Fibrin,  as  usually  obtained,  is  in  the  form  of  brown,  stringy, 
and  "fibrinous"  masses,  which  are  kept  under  glycerin  for  labor- 
atory use.  It  is  insoluble  in  water  or  alcohol.  In  dilute  acid 
(HCl)  or  alkali  solutions,  it  swells  and  ultimately  dissolves, 
although  it  may  be  several  days  before  solution  is  effected.  The 
fibrins  from  the  blood  of  different  animals  differ  in  composition, 
as  indicated  by  marked  differences  in  solubility. 

The  chemistry  of  the  red  and  white  corpuscles  is  more  complex 
and  not  so  well  known  as  the  chemistry  of  the  plasma,  which 
we  have  considered.  The  red  corpuscles  consist  of  a  frame  of 
protoplasm,  also  called  stroma,  which  contains  lecithin,  choles- 
trin,  nucleoalbumin,  and  a  globulin.  (Hammarsten.)  Upon 
and  all  through  the  stroma  is  the  haemoglobin,  which,  together 
with  its  oxygen  compound  oxyhaemoglobin,  is  responsible  for 
the  color  of  the  blood.  Oxyhaemoglobin  may  be  obtained  as 
silky,  transparent  crystals  of  blood-red  color. 

From  hasmoglobin  may  be  derived  the  blood  pigment  hcemo- 
chromogejt,  containing  iron,  and  this  by  oxidation  is  converted 
into  haematin.  The  iron  from  the  blood  may,  by  decomposi- 
tion of  the  pigment  and  subsequent  combination  with  sulphur 
(FeS),  cause  discoloration  of  teeth.  This  is  the  theory  of 
Dr.  Kirk  of  Philadelphia,  and  in  the  author's  opinion  is  per- 
fectly sound,  and  far  more  probable  than  other  explanations 
which  have  been  offered,  but  which  do  not  recognize  the  forma- 
tion of  a  sulphur  compound. 

CO  Haemoglobin.  —  Haemoglobin  forms  with  carbon  monoxid 
(from  water-gas  or  other  sources)  a  definite  and  very  stable 


296  PHYSIOLOGICAL   CHEMISTRY 

compound,  being  even  stronger  than  the  oxyhaemoglobin,  to 
which  reference  has  previously  been  made.  Blood  containing 
carbon  monoxid  haemoglobin  is  of  a  bright-red  color,  which 
darkens  in  the  air  much  more  slowly  than  ordinary  blood. 

Haemin,  or  Teichmann's  haemin  crystals,  is  the  hydrochloric 
acid  compound  of  haematin.  (See  Exp.  206,  page  299,  also 
Plate  VII,  Fig.  2.) 

The  form  of  the  red  corpuscle  is  that  of  a  biconcave  disk 
without  nucleus;  by  action  of  water  it  becomes  swollen,  and 
the  haemoglobin  may  be  washed  away,  leaving  the  "stroma." 
The  diameter  of  the  red  corpuscles  of  human  blood  is  about 
1/3200  of  an  inch.  Of  the  domestic  animals,  the  corpuscles  of 
the  dog  approach  most  nearly  to  the  measurement  of  the  human. 
The  sheep,  horse,  and  ox  have  smaller  corpuscles  than  man, 
while  those  of  birds,  cold-blooded  animals,  and  reptiles  are 
larger  (see  Plate  VII,  Figs.  5  and  6). 

The  white  corpuscles  are  rather  larger  than  the  red,  and 
occur  in  much  smaller  numbers,  a  cubic  millimeter  containing 
about  5,000,000  red  to  7500  white.  The  white  corpuscles  pre- 
sent a  much  greater  diversity  of  character  than  do  the  red. 
They  contain  one  to  four  nuclei,  and  are  capable  of  amoeboid 
movements.  The  white  corpuscles  are  also  called  leucocytes, 
aggregations  of  which  constitute  pus.  The  leucocytes  are  di- 
vided histologically  into  various  classes,  —  lymphocyte,  neutro- 
philes,  eosinophiles,  etc.,  —  according  as  they  are  acted  upon 
by  different  staining-fiuids  or  fulfill  some  particular  office;  but 
these  are  not  to  be  distinguished  chemically. 

Muscle. 

The  chemistry  of  muscle  is  complex.  It  changes  rapidly 
upon  the  death  of  the  animal,  so  much  so  that  the  Hquid  which 
may  be  expressed  from  living  muscle  (or  from  muscle  frozen 
immediately  upon  the  death  of  the  animal)  has  been  called 
muscle  plasma,  in  distinction  from  the  fluid  obtained  in  the 


PLATE  VII.— PHYSIOLOGICAL  CHEMISTRY. 


Fig.  I. 
Edesten. 


Fig.  3. — Fat  Crystals. 
A,  Butter  Crystals;  B,  Lard  Crystals. 


Fig.  5. 

4,  Human  Blood;  B,  Horse  Blood; 

C,  Dog  Blood. 


Fig.  2. 
Teichmann's  Hemin  Crystals. 


Fig.    4. 
A,  Fat  Acid;  B,  Cholesterin. 


■      "  ■  "■(      u 

'^ 

'"  ;.'-o  00 

d 

0    0       / 
0           ^/ 

Fig.  6. 
^,  Frog  Blood;  B,  Chicken  Blood; 
C,  Fish  Blood. 


BLOOD  AND  MUSCLE  297 

same  manner  from  dead  muscle,  which  is  called  muscle  serum. 
The  chemical  reactions  of  these  solutions  differ,  due  to  the 
formation  of  sarcolactic  acid  in  the  dead  muscle.  The  proteins 
differ  in  certain  respects.  Myosin  is  the  most  essential  con- 
stituent of  muscle  plasma,  and  corresponds  to  the  fibrin  of  the 
blood-clot.  It  exists  as  a  parent  protein  myosinogen,  or 
myogen,  from  which  it  may  be  precipitated  by  saturation  with 
salt  or  magnesium  sulphate.  Myosin  has  many  of  the  prop- 
erties of  the  globulins,  but  differs  in  the  very  important  particu- 
lar of  not  being  precipitated  by  dialyzation.  Among  the  more 
important  extractive  bodies  obtained  from  muscle  are  creatin, 
carnin,  inosite,  glycogen,  and  lactic  acid.  Creatin  is  a  xanthin 
body,  being  chemically  a  methyl-guanidin-acetic  acid,  which 
may  appear  in  the  urine  as  creatinin.  (Creatinin  is  creatin 
minus  H2O.) 

Carnin  is  a  white  crystalline  substance  obtained  from  meat 
extract  and  converted  by  oxidation  induced  or  produced  by 
nitric  acid,  chlorin  or  bromin  into  hypoxanthin  or  sarkin.  Its 
chemical  constitution  is  not  positively  known. 

Inosite,  C6H12O6+H2O,  is  a  hexahydroxybenzene,  C6H6(OH)6 
+  H2O.  It  has  a  sweet  taste,  and  was  formerly  erroneously 
classed  with  the  carbohydrates.  It  is  capable  of  yielding  lactic 
and  butyric  acids  ( ?) . 

Glycogen  occurs  in  sHght  amounts  in  muscle,  but  decomposes 
after  death,  with  formation  of  a  reducing  sugar.  (Compare 
page  264.) 

Lactic  Acid  is  a  constituent  not  only  of  muscle  but  also  of 
various  glands,  of  the  bile,  and  of  blood.  For  the  chemistry 
of  this  substance,  see  page  220. 


298  PHYSIOLOGICAL  CHEMISTRY 

Laboeatory  Exercise  LXVIII. 
Experiments  on  Blood. 

Exp.  200.  Test  the  reaction  of  blood  with  a  piece  of  Htmus- 
paper  which  has  been  previously  soaked  in  a  concentrated  NaCl 
solution.     To  what  is  reaction  due  ? 

Exp.  201.  Blood-corpuscles.  —  (a)  Examine  a  drop  of  blood 
under  the  microscope.     Sketch  the  red  and  white  corpuscles. 

{h)  Note  the  difference  between  the  corpuscles  of  mammals 
and  those  of  birds  and  reptiles. 

(c)  Note  the  effect  upon  the  red  corpuscles  produced  by  the 
addition  of   (i)  water,  (2)  a  concentrated  solution  of  salt. 

Exp.  202.  Hcemoglobin  Crystals.  —  Place  a  drop  of  de- 
fibrinated  rat's  blood  on  a  sKde;  add  a  drop  or  two  of  water; 
mix,  and  cover  with  a  cover-glass.  Sketch  the  crystals  which 
separate  after  a  few  minutes.  Or  instead  of  above  add  a  few 
drops  of  ether  to  some  blood  in  a  test-tube;  shake  thoroughly 
until  the  blood  becomes  "laky,"  and  then  place  the  tube  on 
ice  till  crystals  appear. 

Exp.  203.  A  spectroscope  will  be  found  ready  for  use  in  the 
laboratory,  and  the  absorption-bands  given  by  oxyhaemoglobin 
and  haemoglobin  will  be  demonstrated.  The  student  may  pre- 
pare solutions  for  examination  as  follows: 

(a)  Oxyhcemoglohin.  —  Use  dilute  blood  (one  part  of  de- 
fibrinated  blood  in  fifty  parts  of  distilled  water). 

(&)  Hcemoglobin  (reduced  haemoglobin) .  —  Add  to  blood  a  few 
drops  of  strong  ammonium  sulphid,  or  one  or  two  drops  of 
freshly  prepared  Stokes's  reagent.*  Note  the  change  in  color 
produced  by  the  addition  of  the  reducing  agent.  Shake  with  air 
and  note  the  rapid  change  to  oxyhaemoglobin. 

(c)  Hcemochromogen.  —  To  a  little  of  the  haemochromogen, 
reduced  with  ammonium  sulphid,  add  a  few  drops  of  concen- 

*  Stokes's  reagent  consists  of  two  parts  of  ferrous  sulphate  and  three  parts  of 
tartaric  acid  dissolved  in  water  and  ammonia  added  to  distinct  alkaline  reaction. 
There  should  be  no  permanent  precipitate. 


BLOOD  AND  MUSCLE  299 

trated  NaCl,  and  note  the  spectrum  of  reduced  haematin  or 
haemochromogen. 

{d)  Carbonmonoxid  Hcemoglohin.  —  Pass  a  current  of  illumin- 
ating gas  through  a  dilute  oxyhaemoglobin  solution  for  a  few 
minutes  and  filter.  Note  the  change  of  color.  Try  the  effect  on 
the  solution  of  (i)  ammonium  sulphid;  (2)  Stokes's  reagent; 
(3)  shaking  with  air.     Note  the  stability  of  the  compound. 

Exp.  204.  Take  the  specific  gravity  of  blood  by  filHng  a  test- 
tube  one-half  full  of  benzene;  add  one  drop  of  blood,  and  then 
add  chloroform,  a  drop  at  a  time,  with  careful  but  thorough  mix- 
ing, until  the  drop  of  blood  floats  at  about  the  middle  of  the 
mixture,  indicating  that  the  gravity  of  the  mixture  and  of  the 
blood  are  the  same.  The  specific  gravity  of  the  benzene  and 
chloroform  may  be  taken  in  any  convenient  way. 

Exp.  205.  Make  the  guaiacum  test  for  blood  on  a  sample  of 
dried  blood;  also  on  potato  scrapings.     The  method  is  as  follows: 

To  a  little  clear  solution  of  blood  or  material  obtained  from 
potato  scrapings,  add  some  fresh  tincture  of  guaiacum ;  then  add 
a  few  drops  of  an  ethereal  solution  of  hydrogen  peroxid,  shake 
the  mixture  and  note  the  blue  color  obtained. 

From  these  two  tests  what  do  you  gather  about  the  value  of 
the  guaiacum  test  for  blood,  and  what  is  probably  the  cause  of 
the  coloration? 

Exp.  206.  Hcemin  Crystals  {Teichmann's  Test). — Place  a 
bit  of  powdered  dried  blood  on  a  glass  slide;  add  a  minute 
crystal  of  NaCl  (fresh  blood  contains  sufficient  NaCl)  and  two 
drops  of  glacial  acetic  acid.  Cover  with  a  cover-glass  and  warm 
gently  over  a  flame  until  bubbles  appear.  On  cooling,  dark- 
brown  rhombic  crystals,  often  crossed,  separate  (chlorid  of 
hcematin).  Similar  crystals  can  be  obtained  by  using  an  alka- 
lin  iodid  or  bromid  in  place  of  NaCl. 

Exp.  207.  Coagulation  of  Blood.  —  Observe  the  phenomena 
of  coagulation  as  it  takes  place  {a)  in  a  test-tube;  {h)  in  a 
drop  of  blood  examined  under  the  microscope.     Explain  fully. 


300  PHYSIOLOGICAL  CHEMISTRY 

Exp.  208.  Proteins  of  Blood-plasma.  —  {a)  Serum-albumin. 
(6)  Serum-globulin.  Using  blood-serum,  separate  and  identify 
these  two  proteins. 

(c)  Fibrinogen.  —  Fibrinogen  is  a  globulin  found  in  blood- 
plasma,  l3mipli,  etc.,  together  with  paraglobuUn.  Like  para- 
globulin  it  responds  to  all  the  general  precipitants  and  tests,  and 
in  addition  gives  the  reactions  with  CO2,  dialysis  and  MgS04. 
It  is  distinguished  from  paraglobuHn  easily  by  two  reactions,  viz., 
its  power  to  coagulate,  i.e.,  to  form  fibrin  when  acted  on  by  fibrin 
ferment,  and  its  temperature  of  heat  coagulation,  which  will  be 
found  to  be  from  56°  to  60°  C. 

Exp.  209.     Fibrin.  —  {a)  Note  its  physical  properties.  / 

{b)  Note  action  of  0.2%  hydrochloric  acid. 

(c)  Apply  the  protein  color  tests. 

Laboratory  Exercise  LXIX. 
Experiments  with  Muscle. 

Exp.  210.  Place  25  grams  of  fresh  finely  chopped  muscle 
in  a  beaker  with  75  c.c.  of  5%  solution  of  common  salt,  and 
allow  to  stand  for  about  one  hour,  with  frequent  stirring.  (In 
the  meanwhile  perform  Exp.  211.)  Then  filter  off  the  liquid 
and  make  the  following  tests  with  the  filtrate : 

{a)  Test  for  proteins. 

(&)  Having  found  proteins,  pour  a  little  of  the  solution  into 
a  beaker  of  water.     Result.     Inference  (myosin). 

(c)  Make  a  fractional  heat  coagulation  in  the  following  man- 
ner (upon  the  care  with  which  the  temperatures  given  are  ad- 
hered to,  depends  the  success  of  the  separation) :  Warm  to  from 
44°  to  50°  C,  and  keep  at  that  temperature  for  a  few  minutes. 
The  coagulum  is  myosin  [synonyms:  paramyosinogen  (Halli- 
burton), musculin  (older  authors)].  In  solutions  the  myosin, 
which  has  the  properties  of  a  globulin,  becomes  insoluble  after  a 
time,  because  it  changes  to  myosinfibrin.  In  heating  the  solu- 
tion as  above,  a  sUght  cloud  may  appear  at  from  30°  to  40°  C. 


BLOOD  AND  MUSCLE  30I 

This  is  due  to  coagulation  of  soluble  myogenfibrin.     Now  filter 
off  the  coagulated  myosin. 

Heat  filtrate  to  from  55°  to  65°  C.  The  coagulum  is  myogen 
(synonym:  myosinogen).  In  spontaneous  coagulation  of  its 
solutions  it  forms,  first,  soluble  myogenfibrin,  and,  finally,  in- 
soluble myogenfibrin.     Filter. 

Heat  to  from  70°  to  90°  C.  Coagulum  is  serum  albumin  from 
the  blood  within  the  muscle,  and  is  not  a  constituent  of  the  muscle 
plasma.     Filter. 

Test  filtrate  for  proteins.  If  it  shows  a  slight  biuret  test, 
this  is  due  either  to  incomplete  precipitation  by  coagulation 
or  to  the  post-mortem  formation  of  albumose  or  peptone  by 
auto-digestion  (autolysis) . 

Exp.  211.  Make  an  aqueous  extract  of  muscle,  and  test  for 
lactic  acid  by  acidulating  with  H2SO4,  extracting  with  ether 
and  testing  the  ethereal  extract  with  very  dilute  ferric  chlorid 
solution.  The  presence  of  lactic  acid  is  shown  by  a  bright- 
yellow  color. 

Exp.  212.  Creatin  may  be  most  conveniently  prepared 
from  a  strong  solution  of  Liebig's  extract.  Dissolve  the  extract 
in  twenty  parts  of  water,  add  basic  lead  acetate  drop  by  drop  to 
avoid  more  than  a  sHght  excess,  then  remove  excess  of  lead; 
concentrate  to  a  syrup  over  a  water-bath  and  allow  to  stand  in 
a  cool  place,  when  creatin  crystals  will  separate  out.  Two  or 
three  days'  time  may  be  required  before  the  crystals  are  ob- 
tained. They  may  be  washed  with  88%  alcohol  and  purified 
by  recrystallization  from  water.  Hypoxanthin  and  sarcolactic 
acid  may  be  obtained  from  the  mother  Kquor.* 

Exp.  213.  Creatinin  may  be  prepared  from  creatin  by 
boihng  for  ten  or  fifteen  minutes  with  very  dilute  sulphuric  acid. 
NeutraHze  the  acid  with  BaCOs,  filter,  evaporate  to  dryness  on 
a  water-bath,  and  extract  the  creatinin  with  alcohol.  Upon 
evaporation  the  creatinin  is  obtained  in  the  form  of  crystals. 
*  Lea's  Chemical  Basis  of  the  Animal  Body. 


PART   VII. 

DIGESTION. 


CHAPTER  XXXIII. 

SALIVA    PROPERTIES   AND   CONSTITUENTS. 

The  saliva  is  a  mixed  secretion  from  the  parotid,  submax- 
illary, and  sublingual  glands,  together  with  a  slight  amount 
obtained  from  the  smaller  buccal  glands.  The  chemical  com- 
position of  the  secretion  from  these  various  sources  differs  con- 
siderably, but  from  a  chemical  standpoint  we  are  much  more 
interested  in  the  mixed  saliva  and  its  constituents  than  the 
differences  in  the  product  of  the  various  glands.  The  notable 
differences  are  that  the  mucin  is  practically  wanting  in  the 
parotid  saliva.  The  alkaline  salts  seem  to  be  in  smaller  pro- 
portion in  the  parotid  saliva  than  in  the  other  two.  Potassium 
sulphocyanate  is  a  constituent  of  all  varieties  of  saliva,  although 
more  constantly  present  in  the  submaxillary  and  in  the  sublingual 
than  in  the  parotid.  The  parotid,  on  the  other  hand,  contains 
a  larger  proportion  of  dissolved  gases.  The  data  on  the  com- 
position of  these  varieties  differ  to  a  considerable  extent  and 
comparisons  are  not  wholly  satisfactory. 

The  mixed  saliva  contains,  according  to  Professor  Michaels, 
all  the  salts  of  the  blood  which  are  dialyzable  through  the  salivary 
glands,  and  hence  furnishes  a  rehable  index  of  metabolic  proc- 
esses which  are  being  carried  on  within  the  system.  In  order 
for  this  fact  to  be  of  practical  values,  two  things  are  obviously 
of  prime  importance:  First,  methods  of  analysis  which  are  not 
too  complicated  and  at  the  same  time  conclusive;    second,  a 

302 


SALIVA    PROPERTIES  AND   CONSTITUENTS  303 

knowledge  regarding  the  source  of  the  various  constituents 
found  which  will  enable  us  to  make  a  rational  interpretation  of 
the  results  obtained.  In  both  of  these  fundamentals  we  are  very 
much  hampered  by  lack  of  knov/ledge ;  as  yet  there  is  much  to  be 
desired  in  the  way  of  practical  clinical  tests  for  the  various 
saHvary  constituents,  and  very  much  to  be  learned  as  to  their 
meanings  in  order  to  make  deductions  which  shall  be  conclusive. 
We  are  led  to  believe  from  the  work  of  an  increasing  number  of 
specialists  that  this  subject  of  salivary  analysis  promises  much 
and  is  certainly  worthy  of  careful  investigation. 

The  quantity  of  saliva  secreted  in  twenty-four  hours  is  var- 
iously estimated  from  a  few  hundred  to  1500  c.c;  1200  to  1500 
is  the  more  probable  amount.  The  quantity  is  diminished  in 
fevers,  severe  diarrhoea,  diabetes,  and  nephritis,  by  fear  and 
anxiety,  and  by  the  use  of  atropine.  It  is  increased  by  smoking, 
by  mastication,  by  the  use  of  mercury,  potassium  iodid,  or 
pilocarpin.  The  flow  of  saUva  is  also  increased  by  action  of  the 
sympathetic  nervous  system,  during  pregnancy,  and  by  local 
inflammatory  process. 

Physical  Properties.  —  The  physical  properties  of  saliva  in- 
clude its  appearance,  specific  gravity,  reaction,  color,  and  odor. 

Appearance.  —  The  appearance  is  clear,  opalescent,  frothy, 
or  cloudy;  normal  saliva  is  usually  opalescent.  It  may  become 
turbid  by  precipitation  of  lime-salts  caused  by  the  escape  of 
carbon  dioxid. 

Specific  Gravity.  —  Specific  gravity  ranges  from  1.002  to  1.009, 
the  total  sohds  being  only  from  0.6  to  2.5  per  cent. 

Reaction.  —  The  reaction  is  normally  alkaline  to  litmus- 
paper  or  to  lacmoid.  Normal  saliva,  however,  fails  to  give 
an  alkaline  reaction  with  phenolphthalein,  due  to  the  presence 
of  free  CO2,  which  may  be  present  to  the  extent  of  19  parts  in 
100,  by  volume.  If  the  sample  be  subjected  to  even  a  slight 
degree  of  heat  the  acid  gas  is  expelled;  then  the  usual  pink  color 
may  be  obtained  with  this  indicator.     SaHva  may  be  acid  upon 


304  DIGESTION 

fasting,  particularly  before  breakfast  and  also  after  much  talk- 
ing. Acid  conditions  may  exist  which  are  local  in  their  char- 
acter and  due  to  lactic  acid  fermentation.  Acid  saHvas  may 
also  be  met  with  in  cases  of  rheumatism,  mercury  salivation, 
and  diabetes.  By  exercise  of  the  glands,  as  during  the  chew- 
ing of  food,  the  alkalinity  is  increased;  oftentimes  the  reaction 
changes  from  faintly  acid  to  alkaHne  during  this  process,  the 
proportion  of  alkaline  salts  becoming  greater,  although  the  total 
soUds  as  a  whole  are  slightly  diminished.  This  fact  of  the 
change  in  the  reaction  from  acid  to  alkaline  has  been  explained  by 
ascribing  the  acidity  due  to  fermenting  particles  in  the  mouth; 
the  continued  process  of  chewing  and  swallowing  washes  this 
away,  or,  in  other  words,  the  change  in  reaction  is  a  mechan- 
ical one  rather  than  a  change  of  the  chemical  composition  of  the 
secretion.  This  explanation  seems  to  be  a  superficial  one  and 
without  sufficient  experimental  foundation. 

The  acidity  of  saliva,  as  indicated  at  the  opening  of  this 
paragraph,  is  referred  to  the  behavior  of  the  saliva  to  phenol- 
phthalein,  and  is  in  large  part  due  to  the  presence  of  free  carbon 
dioxid. 

The  sources  of  CO2  in  saliva  are  probably  three.  CO2 
dialyzed  through  the  salivary  glands,  traces  from  carbohydrate 
fermentation,  and  considerable  quantities  absorbed  from  con- 
tact with  expired  air. 

The  saliva  obtained  by  chewing  paraffiin  (a  process  calcu- 
lated to  furnish  the  maximum  amount  from  the  last  two  sources) , 
may  yield  several  times  the  amount  of  free  CO2  that  another 
sample  taken  from  the  same  patient  by  a  saliva  ejector  will  give. 

Acidity  of  saliva  may  be  temporary  when  it  may  be  entirely 
removed  by  drawing  air  through  the  heated  (not  boiled)  sample. 
The  permanent  acidity  may  be  determined  by  titration  of  the 
sample  after  removal  of  CO2. 

The  apparatus  pictured  in  Fig.  19  has  been  used  by  the 
author  for  this  acidity  determination. 


SALIVA    PROPERTIES  AND   CONSTITUENTS 


305 


The  air  is  drawn  from  left  to  right  first  through  a  potash 
bulb  (A)  to  absorb  atmospheric  CO2,  next  through  10  c.c.  of 
saHva  diluted  with  20  c.c.  of  water  contained  in  a  small  Soxhlet 


Fig.  19. 

flask  (B)  whereby  the  CO2  from  the  sahva  is  carried  through  the 
"test-tube  condenser"  and  collected  in  baryta  water  in  the 
Erlenmeyer  flask  (C)  at  the  left.  This  in  turn  is  connected  with 
a  suction  pump  or  aspirator.  The  ''drip  cup"  (D)  has  been 
found  necessary  when  working  with  very  viscid  samples.     The 


3o6  DIGESTION 

thistle  tube  (E)  holds  water  for  maintaining  the  volume  in  {B) 
if  the  condenser  is  not  used. 

The  amount  of  free  CO2  may  be  determined  by  adding  a  stand- 
ard carbonate  solution  (N/ioo  Na2C03)  to  a  volume  of  baryta 
water  equal  to  that  used  in  the  Erlenmeyer  flask  and  then  com- 
paring the  degree  of  turbidity  obtained.  This  may  be  done  by 
viewing  through  flat-bottom  tubes  (shell  tubes)  of  about  20  c.c. 
capacity,  or,  in  many  cases,  better,  by  use  of  the  Duboscq  col- 
orimeter used  for  determination  of  ammonia  (Fig.  20,  page  307). 

Permanent  acidity  is  of  comparatively  rare  occurrence  and 
is  due  either  to  the  presence  of  acid  salts,  such  as  NaH2P04,  or 
slight  amount  of  organic  acids  possibly  combined  as  acid  meta- 
protein.  This  acidity  and  its  clinical  significance  is  at  present 
under  investigation. 

Color.  —  Saliva  is  usually  colorless  when  fresh,  but  upon 
standing  for  twenty-four  hours  may  assume  various  tints, 
which  are  developed  from  constituents  derived  from  bile.  (Pro- 
fessor Michaels.)  Saliva  may  be  colored  red  or  brown  by  the 
presence  of  blood  or  blood  pigments,  but  in  such  cases  the 
source  of  the  color  is  usually  local  and  easily  discovered. 

Odor.  —  Normal  saliva  is  practically  odorless.  In  cases  of 
pyorrhoea  there  is  usually  a  pecuHar  fetid  odor  easily  recognized. 
In  other  pathogenic  conditions  the  odor  may  be  slightly  ammonia- 
cal,  or  occasionally  resemble  the  odor  of  acetone  or  garlic. 

Constituents.  —  We  should  here  distinguish  carefully  be- 
tween saliva  proper  and  sputum.  The  constituents  of  sputum 
are  derived  from  the  air-passages  rather  than  from  the  salivary 
glands,  and  are  not  at  present  under  consideration.  Among 
the  normal  constituents  of  saliva  are  included  mucin,  albumin, 
ptyaHn,  also  oxydizing  enzymes,  ammonium  salts,  nitrites, 
potassium  sulphocyanate,  alkaline  phosphates,  and  chlorids,  with 
traces  of  carbonates;  and,  in  the  sediment,  epithelium  cells, 
occasional  leucocytes,  and  fat  globules.  The  abnormal  con- 
stituents  will   include   glycogen,   urea,    dextrin,    rarely   sugar, 


SALIVA    PROPERTIES   AND   CONSTITUENTS 


307 


•cholesterin,  derivatives  from  bile,  lecithin,  xanthin  bodies  or 
alkaline  urates,  acetone,  lactic  acid,  and  crystalline  elements 
resulting  from  insufficient  oxidation  or  perverted  glandular  func- 
tion.    These  latter  are  recognizable  by  the  micropolariscope. 


Fig.  20.  —  Colorimeter. 

Mercury  and  lead  may  also  be  found  in  saliva  in  cases  of  poison- 
ing by  salts  of  these  metals. 

Mucin.  —  The  secretion  from  the  parotid  gland  contains 
practically  no  mucin,  but  the  sublingual  saliva  contains  large 
amounts.     Mucin  is,  according  to  Simon,  the  most  important 


3o8  DIGESTION 

constituent  of  the  saliva,  not  excepting  ptyalin.  The  various 
glands  contributing  salivary  mucin  do  not  in  all  probability 
furnish  just  the  same  kind  of  protein;  moreover,  the  mucin 
from  different  individuals  seems  to  vary  in  composition  and 
properties,  some  yielding  more  abundant  acid  decomposition 
products  than  others  (see  article  by  W.  D.  Miller,  in  Dental 
Cosmos  for  November,  1905),  while,  according  to  Professor 
Michaels,  the  mucin  varies  much  in  the  same  individual  in 
health  and  disease.  The  changes  in  the  characteristics  of 
salivary  mucin  have  been  studied  but  little,  and  the  investiga- 
tion of  these  changes,  as  indications  of  diathetic  states,  promises 
much. 

An  excess  of  mucin  in  the  saliva  tends  to  an  increase  of 
bacterial  growth,  from  the  fact  that  it  furnishes  increased 
facilities  for  multiplication;  it  may  also  give  rise  to  mucic  acid, 
which,  according  to  Dr.  G.  W.  Cook  of  Chicago,  is  a  probable 
factor  in  tooth  erosion.  (See  Dental  Review,  May,  1906,  page 
461.) 

Albumin. — Albumin  is  present  in  very  small  quantities, 
increased  during  mercurial  ptyalism,  usually  in  cases  of  pyor- 
rhoea, and,  according  to  some  authorities,  in  various  albuminu- 
rias. It  may  be  detected  by  usual  methods  after  the  separation 
of  mucin. 

"According  to  Vulpian,  the  quantity  of  albumin  is  increased 
in  the  saliva  of  albuminurics  of  B right's  disease.  The  saliva 
of  a  patient  with  parenchymatous  nephritis  had  mucin  0.253 
and  albumin  0.182  per  cent.  The  saliva  of  another  patient, 
with  albuminuria  of  cardiac  origin,  contained  mucin  0.45 
albumin  0.145  per  cent.  In  a  healthy  man  there  was  found 
mucin  0.320,  albumin  0.05  per  cent.  This  fact  has  been  con- 
firmed by  Pouchet,  who  found  these  substances  in  greater  quan- 
tities. "  * 

*  Dr.  Joseph  P.  Michaels.  S.  S.  White's  reprint  of  paper  read  before  Inter- 
national Dental  Congress,  Paris,  1900. 


SALIVA    PROPERTIES  AND   CONSTITUENTS  309 

Ptyalin.  —  Ptyalin  is  the  principal  ferment  of  the  saKva ;  it 
converts  starch,  by  hydrolysis  through  the  various  dextrins 
(page  264),  to  maltose.  The  maltose  in  turn  is  converted  into 
glucose  by  a  second  ferment,  known  as  maltase,  which  exists 
in  saliva  in  very  small  quantities. 

The  activity  of  ptyalin  is  greatest  at  a  temperature  of  40°  C. 
Very  faintly  acid  saliva  is  the  best  media.  Neutral  and  faintly 
alkaline  salivas  are  next  in  order.  \ 

The  amylolytic  power  of  a  given  sample  of  saliva  may  be 
determined  by  the  action  on  dilute  starch  paste.  In  making 
comparative  tests  it  is  essential  that  the  conditions  under  which 
the  ptyalin  is  allowed  to  act  should  be  exactly  the  same,  especially 
as  regards  the  temperature  and  duration  of  the  process.  A 
slight  variation  in  the  strength  of  the  starch  solution  is  of  no 
consequence,  as  starch  is  supposed  to  be  in  excess.  (See  Exp. 
214  on  page  327,  also  method  on  page  322.) 

Ammonium  Salts.  —  Ammonium  salts  occur  chiefly  as  chlorid, 
probably  to  some  extent  as  sulphocyanate,  and  occasionally  as 
oxalate.  Professor  Michaels  says  that  ammonia  must  be  con- 
sidered as  a  more  completely  oxidized  form  of  nitrogen  than  urea ; 
hence  its  relative  increase  is  observed  in  all  diseases  which  occa- 
sion an  excess  of  nitrogen  and  urea,  as  in  tuberculosis  and  all 
hypoacid  diatheses.  There  is  a  decrease  of  ammonia  whenever 
the  nitrogen  fails  to  reach  the  stage  of  oxidation  represented  by 
urea.  This  condition  is  accompanied  by  uric  acid  and  other 
products  of  deficient  oxidation,  and  characterizes  the  hyperacid 
state.  The  ammonia  may  be  detected  by  a  microscopical  ex- 
amination of  the  dried  sahva,  although  the  ammonium  salts 
do  not  polarize  light  (Plate  VIII,  Fig.  i,  page  327),  also  by  the 
reaction  with  Nessler's  reagent,  which  produces  a  yellow  color. 

Potassium  Sulphocyanate  is  pecuKarly  a  constituent  of  the 
saliva,  although  it  occurs  in  traces  in  the  blood,  urine,  etc. 
In  a  state  of  health,  according  to  Dr.  Michaels,  the  ammonium 
salts  and  the  sulphocyanates  are  present  in  very  slight  amounts, 


3IO  DIGESTION 

and  the  color-tests,  with  Nessler's  solution  and  with  ferric  chlorid, 
respectively,  are  of  about  equal  intensity.  In  the  hyperacid 
state  the  sulphocyanates  are  in  excess  of  ammonia,  while  in 
hypoacid  conditions,  the  ammonia  exists  in  the  greater  quan- 
tity. Sulphocyanate  is  detected  by  means  of  ferric  chlorid, 
and  distinguished  from  meconates  and  acetates,  as  indicated 
by  Exp.  216  page  329.  The  sulphocyanates  are  normal  con- 
stituents of  saliva,  and  consequently  always  present.  According 
to  A.  Mayer  (Deutsch.  arch.  f.  klin.  med..  Vol.  79,  No.  394), 
the  sulphocyanates,  without  doubt,  result  from  the  decomposi- 
tion of  proteins,  and  exist  in  the  urine  in  quantities  variously 
estimated  from  20  to  80  milligrams  per  liter,  while  in  saliva  it 
has  been  estimated  from  60  to  100  milligrams  per  liter.  Professor 
Ludholz  of  the  University  of  Pennsylvania  says  that  the  sulpho- 
cyanates are  eliminated  in  increased  amounts  in  conditions 
where  there  is  a  lack  of  oxygen  in  the  system,  thus  corrobo- 
rating statements  of  Professor  Michaels  (see  Ammonia).  Dr. 
Fenwick  (Lancet,  1877,  Vol.  II,  page  303)  demonstrated  that 
the  quantity  of  KCNS  was  directly  dependent  upon  the  bile 
salts  in  the  blood.  He  found  an  increase  of  the  salt  in  liver 
disorders  attended  with  increase  of  bile  salts  in  the  blood,  and 
marked  increase  in  jaundice.  In  gout,  rheumatism,  and  con- 
ditions producing  pyorrhoea,  it  is  also  claimed  to  be  present  in 
considerable  quantity. 

The  sulphocyanates  are  usually  present  in  more  than  normal 
quantity  in  the  saliva  of  people  addicted  to  smoking  tobacco.* 
The  claim  has  been  made  for  this  salt  that  it  exerts  a  specific 
antiseptic  action  toward  bacteria. 

While  the  sulphocyanates,  or,  in  fact,  any  salt  in  sufhcient 
concentration,  will  have  an  inhibitory  action  on  the  growth  of 
bacteria,  it  is  rather  doubtful  if  this  is  the  particular  office  of 
KCyS  in  the  saliva. 

Nitrites.  —  That  nitrites  exist  in  most  salivas  is  without  ques- 

*  See  article  by  Dr.  J.  Morgan  Home  in  Jour,  of  the  Allied  Societies,  Vol.  4. 
Ms.  3,  p.  183. 


SALIVA    PROPERTIES   AND  CONSTITUENTS  311 

tion.  So  far  as  we  know  at  present,  the  nitrites  are  apparently- 
incidental,  and  occur  as  intermediate  products  in  the  oxidation 
of  ammonia  to  nitrates,  just  as  they  do  otherwise  in  nature  out- 
side of  the  animal  body. 

It  is  not  at  all  improbable  that  the  proportion  of  nitrates  is 
dependent  upon  activities  of  the  oxidases.  This  has,  in  some 
cases  at  least,  been  proven  to  be  the  case,  as  the  same  sample 
of  saliva  has  frequently  given  steadily  diminishing  quantities 
of  nitrates  until  they  have  wholly  disappeared  in  cases  contain- 
ing active  oxidizing  enzymes. 

Oxidases.  —  As  a  result  of  the  work  of  Dr.  C.  F.  Mac- 
Donald  in  the  author's  laboratory,  the  following  conclusions  were 
reached  regarding  these  enzymes: 

First.  That  human  mixed  saliva  contains  an  oxidizing 
enzyme  distinct  from  ptyahn. 

Second.  That  the  enzyme  exhibits  the  properties  of  both  an 
oxydase  and  a  peroxydase. 

Third.  That  it  is  a  product  of  the  body  (probably  glandu- 
lar) metabolism  and  may  be  increased  in  quantity,  or  activity  by 
mastication. 

Fourth.  That  it  is  more  resistant  to  heat  than  ptyahn,  but 
more  easily  destroyed  by  acids. 

Fifth.  That  the  color  obtained  with  a  freshly  prepared  1%  so- 
lution of  pyrocatechol  is  sufficient  test  for  this  enzyme  in  saliva. 

The  test  for  oxidizing  enzymes  may  be  made  with  the  pyro- 
catechol as  given  on  page  323 ;  also  by  the  use  of  phenolphthalin 
(reduced  phenolphthalein) .  This  last  reagent  has  recently  been 
rendered  available  by  the  work  of  Dr.  H.  L.  Amoss,  Harvard 
Medical  School,  who  has  given  us  a  concise  and  simple  method 
for  its  preparation.     (Jour.  Biolog.  Chem.,  191 2.) 

Phosphates  and  Carbonates.  —  These  salts  are  probably  pres- 
ent in  both  acid  and  neutral  forms ;  that  is,  the  phosphate  may 
exist  as  Na2HP04  also  as  NaH2P04,  and  at  times  both  of  these 
may  be  present  at  once.     The  acid  carbonate,  NaHCOs,  is  an 


312  DIGESTION 

undoubted  constituent,  while  the  neutral  carbonate  is  present  in 
only  very  shght  quantities,  if  at  all.  Chittenden  says  that  mixed 
human  saliva  contains  normally  no  sodium  carbonate  whatever. 

As  explained  by  Dr.  Kirk,  the  normal  reaction  by  which 
overacidity  of  the  blood  is  taken  care  of  by  renal  epithelium 
is  H2CO3  +  Na2HP04  =  NaHsPOi  +  NaHCOg,  and  when  con- 
ditions are  such  as  to  produce  larger  quantities  of  carbonic  acid 
than  the  kidneys  can  eliminate  in  accordance  with  the  above 
reaction,  there  is  an  increased  acidity  of  the  saliva  as  well  as  of 
the  urine.*  In  the  hypoacid  individual,  the  so-called  alkaline 
sodium  phosphate,  Na2HP04,  is  present  in  the  greater  quantity. 
In  diabetic  patients,  sugar  has  very  rarely  been  found  in  the 
saliva;  one  case  coming  under  the  observation  of  the  author 
was  that  of  a  woman  of  middle  age,  with  diabetes  of  long  stand- 
ing, with  8%  of  sugar  in  the  urine,  and  from  this  case  there  were 
obtained  a  very  few  osazone  crystals  by  subjecting  a  consider- 
able quantity  of  saliva,  after  concentration,  to  the  phenyl- 
hydrazine  test. 

Urea  has  been  repeatedly  found  in  the  saliva  of  patients 
suffering  from  chronic  nephritis. 

Acetone  is  of  quite  frequent  occurrence  in  the  saliva.  In 
diabetic  patients  this  substance  is  often  present  in  compara- 
tively large  amounts,  sometimes  sufficient  for  the  detection  of 
the  acetone  by  its  characteristic  odor.  Acetone  may  appear  in 
the  saliva  when  it  is  not  present  in  the  urine.  In  such  cases  it 
has  usually  resulted  from  disordered  digestion  and  a  consequent 
faulty  metaboKsm.  (For  further  consideration  of  acetone,  see 
Urine.) 

Cholesterin  and  lecithin  have  been  found  by  Professor 
Michaels  in  pathological  saHva,  and  leucin  has  been  found  by 
Michaels  in  a  case  of  lupus  and,  according  to  Novey,  in  a  case 
of  hysteria. 

Of  the  crystalline  salts  which  may  be  separated  by  evapora- 

*  International  Dental  Journal,  February,  1904. 


SALIVA   PROPERTIES  AND  CONSTITUENTS  313 

tion  of  dialyzed  saliva,  the  sodium  oxalate  and  the  lactates  and 
acid  lactates  of  Hme  and  magnesia  are  of  the  most  impor- 
tance and  have  been  the  most  thoroughly  studied.  As  these 
salts  may  likewise  be  separated  from  urine  their  significance  will 
be  studied  under  that  head. 


CHAPTER  XXXIV. 
ANALYSIS   OF   SALIVA. 

The  analysis  of  saliva  may  be  taken  up  from  two  distinct 
standpoints,  and  considering  our  present  lack  of  positive  knowl- 
edge on  this  subject  it  may  for  a  while  be  expedient  so  to  study 
it.  First,  we  will  study  a  few  tests  of  saliva  of  such  a  character 
that  they  may  be  made  with  simple  apparatus,  and  which  might 
be  used  by  any  dental  practitioner  with  sufficient  time  and  interest, 
to  contribute  to  our  general  knowledge;  secondly,  we  may  study 
saliva  by  accurate  laboratory  methods  which  are  not  available 
for  general  use,  but  which  are  necessary  for  the  establishment  of 
positive  data,  and  in  fact  necessary  for  an  intelHgent  schedule 
of  tests  under  division  I. 

At  least  two  methods  are  therefore  to  be  considered.  The 
second  method  should  include  the  standard  methods  of  the 
National  Association  but  of  course  is  not  necessarily  confined 
to  them. 

We  shall  introduce  a  third  method  in  some  cases,  which  will 
be  supplementary  to  the  second. 

As  it  is  quite  important  that  the  division  of  salivary  analysis 
into  these  three  methods  be  clearly  understood  the  following 
definite  classification  is  given. 

Methods  marked  I  are  in  large  part  taken  from  Professor 
Michaels'  methods,  and  are  the  simplest  methods  applicable  to 
small  amounts.  They  will  give  results  of  various  degrees  of 
value,  but  may  be  applied  in  a  few  moments  by  any  dentist. 

Methods  marked  II  are  those  given  by  Dr.  Ferris  and 
adopted  by  the  National  Dental  Association  at  its  annual  meet- 
ing in  191 1,  and  reported  in  the  Dental  Cosmos  for  November 
of  that  same  year,  on  pages  1295,  etc. 

314 


ANALYSIS  OF  SALIVA  315 

Methods  marked  III  are  those  which  the  author  beheves  to 
be  the  most  accurate  and  the  most  satisfactory  in  exhaustive 
determinations. 

Physical  properties  of  the  saliva  should  first  be  noted.  In 
method  I,  the  color  and  appearance  of  the  perfectly  fresh  sample 
is  to  be  carefully  compared  with  the  appearance  and  color  after 
standing  for  forty-eight  hours  in  a  small,  tightly  covered  vial. 
The  color  may  be  yellowish,  greenish,  or  brown,  according  to 
the  variety  of  the  derivative  of  bihverdin  from  which  the  color 
is  obtained.*  The  general  appearance  may  also  change  inde- 
pendently of  any  color.  A  saliva  that  is,  when  fresh,  hypoacid 
in  character,  is,  after  forty-eight  hours,  usually  markedly  opales- 
cent and  of  offensive  odor,  while  a  hyperacid  saHva  may  have, 
become  clear  or  cloudy  but  without  odor. 

By  method  II,  we  should  add  to  this  examination  a  viscosity 
test  which  will  be  of  value  as  indicating  the  amount  of  mucin,  as 
probably  the  mucin  content  affects  the  viscosity  more  than  any 
one  constituent. 

The  viscosity  may  be  determined  by  use  of  the  apparatus 
pictured  in  Fig.  21  (page  316). 

The  essential  features  of  the  viscosimeter  are  a  straight  grad- 
uated tube  with  the  constriction  (c)  jacketed  so  that  the  condi- 
tions under  which  a  given  sample  will  pass  through  the  opening 
will  always  be  under  absolute  control. 

The  apparatus  is  standardized  by  partly  filling  with  dis- 
tilled water  in  which  the  bulb  of  a  thermometer  is  immersed. 

The  temperature  of  the  distilled  H2O  is  brought  to  25°  C.  The 
thermometer  is  removed  to  facilitate  reading  and  from  5  to  10 
c.c.  of  the  liquid  are  allowed  to  run  out,  the  time  consumed 
being  accurately  determined  by  a  stop  watch. 

The  viscosity  of  saHva  is  determined  in  the  same  way,  except 
that  this  sample  must  be  strained  through  a  very  fine  brass 

*  Dr.  Joseph  P.  Michaels.  S.  S.  White's  reprint  of  paper  read  before  Inter- 
national Dental  Congress,  Paris,  1900. 


Fig.  21. 


316 


ANALYSIS  OF  SALIVA 


317 


sieve  (100  meshes  to  the  inch)  to  prevent  clogging  of  the  appa- 
ratus. 

If  the  constriction  of  the  graduated  tube  is  sufficiently 
great,  i.e.,  the  opening  sufficiently  small,  comparison  may  be 
made  by  counting  drops  delivered  in  a  given  time.  This  is 
not  advised,  as  there  is  much  greater  difficulty  in  obtaining 
the  saHva  free  enough  from  suspended  particles  so  as  not  to 
clog  the  tube. 

The  inner  tube  should  always  be  filled  to  the  same  mark  in 
the  determination  as  that  used  in  the  standardization  of  the 
instrument. 

The  reaction  may  be  taken  in  method  I  by  the  simple  use 
of  litmus  paper.  This  test  has  a  general 
value,  and  is  sufficient  to  detect  extreme 
conditions.  Our  second  method  should 
be,  in  this  case  as  in  most  others,  a  quan- 
titative one,  and  the  degree  of  alkalinity 
should  be  determined  by  titration  with 
N/20  or  N/ioo  acid,  using  a  strong  prac- 
tically neutral  litmus  solution  as  an  in- 
dicator. The  degree  of  acidity,  using  N/20 
or  N/ioo  alkali  and  neutral  phenol- 
phthalein  as  an  indicator,  should  be  deter- 
mined next.  Then  the  reaction,  after  driv- 
ing off  carbon  dioxid,  should  be  ascertained. 
The  permanent  acidity,  if  such  exists, 
should  be  found  a  useful  factor  in  the  study 
of  Dental  Caries  and  may  be  determined 
by  the  apparatus  pictured  on  page  305. 

Specific  Gravity  may  be  taken  (Method  I)  by  an  ordinary 
urinometer  or  a  specific  gravity  bulb  if  the  quantity  is  sufficient, 
the  reading  to  be  made  from  beneath  the  surface  of  the  liquid. 
If  the  quantity  of  the  sahva  is  small,  it  may  be  diluted  with  an 
equal  volume  of  water,  and  the  last  two  figures  multiplied  by 


Fig.  22.  —  Pyknometer. 


3i8 


DIGESTION 


Fig.  23. 


two  will  give  the  gravity  of  the  undiluted  sample,  or  the  gravity 

may  be  taken  by  the  pyknometer  in  which  the  bulb  of  the  instru- 
ment is  filled  with  sahva  accurately  to  the  mark  M  (Fig.  22), 

and  then  the  reading  of  course  on  this  instrument  will  be  from  the 

bottom  up,  and  the  lower  the  bulb 
sinks  the  greater  will  be  the  gravity 
of  the  sample.  This  method,  claimed 
to  be  devised  by  S.  A.  De  Santos 
Saxe,  M.  D.,  for  use  in  examination 
of  urine,  has  been  suggested  by  Dr. 
Ferris  and  adopted  by  the  National 
Dental  Association  as  an  official 
method. 
For  very  accurate  work  the  use  of  specific  gravity  bottles  is 

recommended.     These  may  be  obtained  holding  one,  two  and 

five  cubic  centimeters  (Fig.  23),  and  with  an 

accurate  balance  of  course  the  gravity  can 

be  accurately  obtained. 

Thiocyanate    (Sulphocyanate)    Tests.  — 

(Method  I.)       To  a  large  drop  of  saliva  on 

a  white  porcelain  surface,   add  about  half 

as  much   5%  ferric   chlorid,   acidified  with 

HCl.     A   reddish    coloration   indicates    the 

presence  of  thiocyanate.        "(Method  II.) 

Use  a  colorimetric  scale  (Ferris  and  Schra- 

dieck),  place  i  c.c.  of  the  specimen  in  tube 

A;  I  c.c.  of  1/2000  ammonia  sulphocyanate 

in  tube  B  (Fig.  24) ;  add  two  drops  of  a  5% 

ferric  chlorid    solution    to    each  tube,  add 

aquo  distillata  in  tube  B,   until  its  color 

matches  that  of  the  specimen.     Read   the 

scale  in  thousandths  and  ten  thousandths. 

"Care  must  be  taken  to  have  the  bottom  of  the  meniscus 

on  the  line.     If  these  tubes  are  introduced  in  the  colorimeter, 


Fig.  24.  —  Sulphocyanate 
Tubes. 


ANALYSIS  OF  SALIVA  319 

the  readings  can  be  made  more  accurately.     If,  later,  diacetic 
acid  ester  is  found,  a  correction  is  made  in  the  finding. " 

A  much  more  accurate  method  than  either  of  these  is  by  use 
of  the  Duboscq  colorimeter,  the  detail  of  the  method  being  as 
follows : 

(Method  III.)  Fifteen  cubic  centimenters  of  a  standard  thio- 
cyanate  solution  is  placed  in  one  tube,  and  in  the  other  a  filtered 
mixture  of  equal  parts  of  saliva  and  alcohol  made  fairly  acid 
with  HCl.  Then  two  or  three  drops  of  acid  ferric  chlorid  are 
added  to  each  tube,  and  the  color  compared.  Scale  on  the  back 
of  the  instrument  makes  it  possible  for  very  accurate  deter- 
minations of  quantity  of  the  color  compound  in  the  unknown 
solution. 

Ammonium  Salts.  —  (Method  I.)  To  a  drop  of  saliva  add 
one  drop  of  Nessler's  reagent:  a  yellow  to  brown  color  shows  the 
presence  of  ammonium  salts.  If  a  precipitate  forms  by  the 
addition  of  Nessler's  reagent,  it  indicates  either  a  large  amount 
of  ammonia  or  the  presence  of  urobilin.  If  due  to  urobilin  the 
precipitate  is  of  a  rose  color  after  desiccation.  Ammonium  salts 
are  usually  seen  in  the  evaporated  drop  examined  by  polarized 
light.     (Plate  VIII,  Fig.  i.) 

(Method  II.)  Add  one  drop  of  neutralized  1%  solution  of 
phenolphthalein  to  2^  c.c.  saliva,  and  titrate  with  N/40  NaOH 
solution  to  a  permanent  color  of  faintest  pink.  Ten  times  the 
number  of  cubic  centimeters  of  NaOH  used  gives  the  acid  index, 
since  N/40  :N::2.5c.c.  iiooc.c,  and  the  acidity  is  expressed 
in  parts  per  liter  (1000  c.c). 

Now  add  to  the  above  i  c.c.  of  neutralized  formalin.  The 
pink  color  disappears,  because  the  formaHn  spKts  off  ammonia 
from  the  organic  matter,  liberating  free  acids.  Titrate  again  to 
find  the  amount  of  combined  acids  thus  liberated,  and  multiply 
the  reading  by  10  as  before. 

Total  acidity  is  obtained  by  adding  the  two  findings. 


320 


DIGESTION 


Amino-acids  calculated  as  ammonia  may  be  obtained  by 
multiplying  the  second  findings  by  0.0017, 

(Method  III.)  A  modification  of  Dr.  FoHn's  ammonia  test 
in  urine,  using  the  Duboscq  colorimeter. 

Measure  out  10  c.c.  of  saliva  in  a  large  Jena  test-tube.  Add 
2  c.c.  of  a  solution  containing  {a)  potassium  oxalate,  (b)  potassium 
carbonate  (15%  of  each).  By  means  of  an  air  cur- 
rent, drive  the  ammonia  through  a  Folin  absorption- 
tube  (Fig.  25)  into  a  100  c.c.  wide-mouth  bottle 
containing  2  c.c.  N/io  HCl,  and  about  30  c.c.  water. 
In  20  minutes,  aU  the  ammonia  should  have  gone  over. 
Remove  the  delivery-tube,  rinsing  it  with  water, 
and  transfer  contents  of  bottle  to  100  c.c.  measuring 
flask,  rinsing  with  sufficient  water  to  make  total 
volume  about  60  c.c. 

Pipette  out  i  c.c.  of  standard  ammonium  sul- 
phate into  another  100  c.c.  measuring  flask  and 
dilute  with  water  to  about  60  c.c. 

Nesslerize  both  solutions   simultaneously  in   the 

following  manner.     Provide  two  small  beakers  (100 

c.c.)  and  place  from  10  to  15  c.c.  of  distilled  water 

in  each.    Add  to  each  5  c.c.  of  Nessler's  reagent. 

Mix  the  reagent  with  water,   and  add  immediately 

to  the  ammonia  solutions.     Add  about  one-third  of 

the  diluted  Nessler  reagent  at  a  time,   and  shake 

after  each  addition. 

Fill  both  flasks  up  to  mark  with  distilled  water,  mix  and 

compare  the  colors  by  means  of  a  Duboscq  colorimeter  (Fig.  20, 

page  307). 

Urea.  —  Reagent,  sodium  h3^obromite  as  used  for  urea  in 
urine  analysis  (Appendix,  page  380). 

Fill  the  tube  of  a  Ferris  modified  Doremus  ureometer  with  a 
saturated  salt  solution.  Close  the  stopper,  and  add  i  c.c.  of 
saliva  to  the  upper  tube.    Allow  this  to  run  through  the  stopper 


Fig.  25. 


ANALYSIS  OF  SALIVA  3 21 

carefully,  then  close,  and  add  i  c.c.  of  the  reagent.  When  this 
has  gone  through,  close  the  stopper  quickly,  set  up  the  apparatus, 
and  allow  to  stand  one  hour  or  longer.  Then,  by  gently  tapping, 
cause  any  bubbles  adhering  to  the  sides  of  the  tube  to  rise  to  the 
top,  and  read  the  amount  of  gas  collected.  Each  division  repre- 
sents 0.025. 

Chlorids. —  (Method  I.)  To  a  drop  of  saHva  add  a  small  drop 
of  a  5%  solution  of  neutral  chromate  of  potassium,  K2Cr04.  Mix 
with  a  glass  rod  and  add  one  drop  of  a  1/10%  solution  of  silver 
nitrate.  This  constitutes  the  test  for  chlorin  which,  if  present 
in  normal  quantities,  will  give  a  reddish  precipitate,  gradually 
becoming  white.  Should  the  precipitate  remain  red  it  shows 
the  chlorin  deficient  or  less  than  normal  in  amount.  If  the 
precipitate  rapidly  turns  white,  or  if  a  white  precipitate  is 
formed  to  the  exclusion  of  the  red,  chlorin  is  increased  in  amount. 
High  chlorin  is  indicative  of  hypoacid  diathesis, 

(Method  II.)  To  i  c.c.  of  the  specimen  add  4  c.c.  of  distilled 
water  and  two  or  three  drops  of  potassium  chromate;  then 
titrate  with  N/40  silver  nitrate  solution,  until  the  first  appear- 
ance of  a  permanent  reddish  tinge.  Multiply  the  number  of 
cubic  centimeters  of  nitrate  used  by  0.0886  to  find  the  amount 
of  chlorin. 

Glycogen.  —  (Method  I.)  A  drop  of  saliva  may  be  tested 
for  glycogen  by  the  addition  of  one  drop  of  an  aqueous  solution 
of  iodin  and  potassium  iodid.  This  must  be  left  for  some  time, 
as  the  test  is  not  obtained  until  the  drop  is  dried;  then,  if  the 
color  is  a  feeble  violet  around  the  edge,  glycogen  is  indicated. 
If  the  color  is  a  strong  brown-red  it  indicates  erythrodextrin, 
if  gray  or  black  a  reducing  sugar. 

Phosphates.  —  The  phosphates  in  saliva  are  determined  as 
in  urine  except  that  it  is  necessary  to  modify  the  process  slightly 
as  given  on  page  153. 

Acetone.  —  (Methods  I  and  III.)  In  the  fifth  drop  dissolve 
a  small  crystal  of  potassium  carbonate,   then  add  a  drop  of 


322  DIGESTION 

Gram's  reagent,  when  a  marked  odor  of  iodoform  will  indicate 
the  presence  of  acetone.  Should  this  odor  be  obtained,  it  is 
better  to  repeat  this  test  upon  a  microscope  slide,  and  examine 
carefully  for  the  characteristic  hexagonal  crystals  of  iodoform 
(Plate  V,  Fig.  i,  page  222). 

Nitrites.  —  (Method  I.)  Nitrites  may  be  detected  by  add- 
ing to  a  large  drop  of  saliva  on  porcelain  a  few  drops  of  freshly 
prepared  reagent,  made  by  dissolving  a  very  little  naphthylamin 
chlorid  and  an  equal  amount  of  sulphanilic  acid  in  distilled  water 
strongly  acidulated  with  acetic  acid.  A  purple  coloration  is  a 
test  for  nitrites. 

This  method  could  be  made  quantitative  in  a  manner  simi- 
lar to  the  colorimetric  methods  for  ammonia,  or  thiocyanate 
of  potassium;  but,  at  the  time  of  the  present  writing,  there 
seems  to  be  no  particular  reason  for  this  amount  of  work. 

Amyloljrtic  Enzymes.  —  (Method  II.)*  Preparation  of  starch 
paste.  Put  15  c.c.  of  distilled  water  to  boil.  Meanwhile,  weigh 
out  3  grams  sterile  starch  and  mix  with  6  c.c.  cold  distilled 
water.  Add  drop  by  drop  under  constant  stirring  to  the  boiling 
water,  then  rinse  out  with  5  c.c.  of  distilled  water  any  particles 
of  starch  adhering  to  the  dish  and  add  to  the  boiHng  starch  solu- 
tion. Boil  one  minute  under  constant  stirring.  Cool  to  blood 
temperature  and  add  gradually  4  c.c.  of  N/ioo  iodin  solution. 

This  makes  30  c.c.  of  a  10%  starch  solution,  which,  when 
colored,  is  of  a  dark  blue,  and  can  be  kept  several  days  in  the 
ice-box. 

Filling  the  Tubes.  —  Suck  up  the  paste  into  glass  tubes  of 
1.5  mm.  diameter,  and  cool  in  the  ice-box.  Just  before  using, 
make  a  file  mark  i  cm.  from  the  end  of  the  tube  and  break  off 
the  piece  of  tubing  so  that  it  is  full  of  the  blue  starch  paste. 
Be  sure  that  this  small  tube  is  broken  so  as  to  leave  each  end 
square  and  full  of  paste.     Examine  under  low-power  microscope. 

Determination  of  Enzyme.  —  Immediately  after  delivery  of 

*  Method  II  as  usual  by  Dr.  Ferris  (see  p.  314). 


ANALYSIS  OF  SALIVA  323 

the  specimen,  measure  2  c.c.  of  saliva  into  a  test-tube.  Place 
it  in  the  small  tube  of  starch  paste,  and  heat  the  whole  in  a 
thermostat  at  from  37°  to  38°  C.  for  half  an  hour.  The  enzyme 
of  the  saliva  will  dissolve  the  paste  from  the  ends  of  the  tube, 
leaving  a  blue  column  of  paste  unchanged  in  the  center  of  the 
glass  tube.  After  half  an  hour,  measure  with  a  micrometer 
gauge  the  total  length  of  the  tube  and  the  length  of  the  blue 
starch  paste  column  remaining  undissolved.  The  difference 
between  these  two  measurements  represents  the  amount  of  starch 
digested  by  the  enzyme.  Since  the  quantity  of  ferment  in  any 
fluid  varies  with  the  square  of  the  length  of  the  column  digested, 
the  quantity  of  ferment  in  the  saliva  is  found  by  squaring 
this  difference.     Multiply  by  100  to  give  the  enzymic  index. 

Proteolytic  Enzyme.  —  (Method  II.)  Reagent.  Dissolve  i 
dg.  of  casein  (c.p.)  and  i  gram  sodium  carbonate  in  i  liter  of 
distilled  water.  Mix  i  or  2  c.c.  Fehling's  copper  solution  and 
5  c.c.  Fehling's  alkaHne  solution,  and  add  the  mixture  to  94  c.c. 
of  the  first  solution.     The  color  will  be  a  light  blue. 

Heat  5  c.c.  of  the  reagent  in  the  thermostat  at  from  37°  to 
38°  C.  Then  add  i  or  2  c.c.  saliva,  and  watch  the  color.  If 
there  is  a  strong  reaction,  the  color  will  turn  pink  in  five  seconds, 
indicating  the  presence  of  peptone.  If  the  reaction  is  medium, 
a  lavender  color  will  result,  indicating  albumin.  If  there  is  no 
reaction,  the  color  will  remain  a  dirty  blue,  and  will  indicate 
unsplit  casein. 

Oxidizing  Enzyme.  —  (Oxydase.)  Methods  I  and  III  con- 
sist of  treating  5  c.c.  of  saliva,  diluted  with  an  equal  volume  of 
water,  with  about  i  c.c.  of  a  1%  solution  of  pyrocatechol.  The 
color  obtained  is  a  characteristic  brown,  developing  within 
thirty  minutes. 

Oxydase.  —  (Method  II.)  Take  i  c.c.  of  saliva,  4  c.c.  of 
aqua  distillata,  twelve  drops  of  a  10%  solution  of  H2SO4,  then 
mix  and  add  drop  by  drop  0.5%  water  solution  of  metaphenylene- 
diamin.     If  there  is  no  oxydase,  it  stays  without  color.     If  there 


324  DIGESTION 

is  an  oxydase,  there  is  formed  triaminphenylin,  which  makes  the 
solution  strongly  yellow.  Compare  the  color  formed  with  four 
drops  and  ten  drops  standard  in  aqua  distillata.* 

Mucin  and  Albumin.  —  (Method  I.)  Mucin  may  be  sepa- 
rated after  taking  the  gravity  by  the  addition  of  a  Httle  acetic 
acid.  It  should  then  be  filtered  off,  but  it  will  be  necessary  to 
dilute  and  agitate,  in  order  that  a  fairly  clear  filtrate  may  be 
obtained. 

Albumin  may  be  demonstrated  in  the  filtrate,  from  which 
mucin  has  been  separated  by  underlaying  with  strong  nitric 
acid.  This  is  Heller's  test  for  albumin  in  the  urine,  and  is  best 
performed  in  a  small  wine-glass  with  round  bottom  and  plain 
sides. 

Mucin,  Albumin  and  Sediments.  —  (Method  II.)*  I.  Cen- 
trifuge lo  c.c.  of  the  specimen  of  saHva  for  three  minutes  in  a 
tube  graduated  to  fortieths.  Record  the  amount,  percentage, 
and  color  of  the  sediment.  Pour  off  and  save  the  supernatant 
fluid;  record  its  appearance. 

II.  To  the  precipitate  add  lo  c.c.  of  limewater,  shake  vigor- 
ously, and  let  stand  for  five  minutes.  Shake  again  and  centrifuge. 
The  difference  between  the  total  sediment  and  this  reading  gives 
amount  of  mucin  and  nuclear  albumin  which  the  limewater  has 
dissolved.     Record  the  percentage  of  the  mucin  in  the  sediment. 

III.  To  2  c.c.  of  the  fluid  saved  from  I  add  8  c.c.  distilled 
water.  A  cloudy  appearance  indicates  the  presence  of  globulin. 
Centrifuge,  and  record  the  amount. 

IV.  {a)  To  the  fluid  remaining  from  II  add  lo  drops  of 
glacial  acetic  acid.  A  precipitate  indicates  dissolved  mucin. 
Centrifuge,  and  record  theamoimt  and  percentage  of  mucin. 

{h)  If  the  saliva  is  thin,  and  if  it  gives  only  a  trace  of  dissolved 
mucin  that  settles  easily,  repeat,  using  the  whole  of  the  liquid 
remaining  from  I.  Save  the  liquid,  and  subtract  the  amount 
of  globulin  from  the  percentage  of  the  precipitated  mucin. 

*  Dr.  H.  C.  Ferris. 


ANALYSIS  OF  SALIVA  325 

(c)  If  the  saliva  is  viscid,  and  if  it  becomes  cloudy  in  (a) 
without  the  separation  of  a  precipitate,  take  2.5  c.c.  of  the 
liquid  remaining  from  I,  add  7.5  c.c.  neutralized  95%  alcohol, 
shake  well,  and  let  stand  for  five  minutes.  Then  centrifuge  and 
record  the  amount  of  dissolved  proteins  in  the  saliva.  Pour  off 
and  save  the  Hquid. 

Add  limewater  to  the  precipitate,  shake  well,  let  stand  for 
two  or  three  hours,  and  centrifuge  to  determine  the  amount  of 
mucin  dissolved  from  this  precipitate. 

V.  (a)  To  the  hquid  remaining  from  IV  (a),  or  IV  (b)  add 
I  c.c.  of  10%  solution  of  potassium  ferrocyanid.  If  albumin  is 
present,  the  specimen  will  become  cloudy.  Centrifuge  as  before, 
and  record  the  amount  of  albumin. 

{b)  To  the  Hquid  remaining  from  IV  (c)  add  i  c.c.  nitric 
acid  to  see  if  there  be  a  precipitate. 

Also  to  the  hquid  in  IV  (a),  when  the  precipitate  will  not 
settle,  add  i  c.c.  of  10%  solution  of  potassium  ferrocyanid  and 
centrifuge.  Subtract  the  amount  of  mucin  found  in  IV  (c)  to 
find  the  quantity  of  albumin. 

Total  Solids  and  Ash.  —  (Method  II.)  These  should  be  de- 
termined immediately  upon  the  arrival  of  the  specimen  to  avoid 
error  through  evaporation  of  moisture. 

Use  a  platinum  or  fused  siKca  dish  of  constant  weight  which 
has  been  kept  in  a  desiccator  over  sulphuric  acid.  Weigh  the 
dish  accurately  and  rapidly,  then  introduce  2^  c.c.  of  the  well- 
mixed  specimen  and  heat  in  a  drying  oven,  not  over  100°  C,  for 
two  hours.  Then  place  in  the  desiccator  over  sulphuric  acid 
for  twelve  hours  or  longer,  and  weigh  accurately  and  rapidly. 

The  difference  between  these  weights  represents  the  weight 
of  total  solids.  To  calculate  the  percentage,  divide  by  two  and 
one-half  times  the  specific  gravity. 

Add  to  the  dish  two  or  three  drops  of  fuming  nitric  acid, 
and  heat  over  a  flame,  keeping  the  dish  two  inches  above  the 
top  of  the  flame,  until  the  black  color  has  become  white.     Heat 


326  DIGESTION 

in  the  direct  flame  until  glowing,  place  at  once  in  desiccator  to 
cool  for  one  or  more  hours,  and  weigh.  Calculate  the  percentage 
of  ash  in  same  manner  as  of  total  solids. 

(Method  III.)  Total  sohds  and  ash  are  best  obtained  as 
follows:  evaporate  over  a  water  bath  5  c.c.  of  the  sample  (10  if 
possible)  thoroughly  mixed  with  a  weighed  amount  (half  a  gram) 
of  ignited  magnesium  oxid.  The  weight  of  residue  (less  the 
magnesia)  obtained  by  drying  at  100°  C,  gives  the  total  soUds. 
These  may  be  ignited  until  white  ash  is  obtained  and  again 
weighed.     The  second  weight  (less  magnesia)  gives  the  ash. 

The  use  of  the  magnesium  oxid  serves  to  retain  carbonates 
and  chlorids  in  the  total  sohds  and  the  chlorids  in  the  ash.  It 
also  obviates  the  necessity  of  oxidation  with  nitric  acid,  which 
would  decompose  many  of  the  inorganic  constituents  of  the 
ash. 

To  determine  weight  of  sediment.  Obtain  total  solids  as 
above;  then  if  a  portion  of  the  saliva  is  carefully  filtered  and  the 
solids  determined  in  the  clear  filtrate  by  the  same  method, 
the  difference  between  the  two  determinations  of  solids  will  be 
the  weight  of  sediment,  epithelium,  leucocytes,  etc. 

Crystals  from  the  Dialyzed  Saliva. 

To  obtain  characteristic  crystals,  as  has  been  explained  in 
considering  the  subject  of  micro-chemistry,  uniformity  as  to 
conditions  under  which  the  crystallization  takes  place  is  a 
necessity.  In  the  case  of  sahva,  however,  we  are  not  produc- 
ing new  compounds,  but  simply  searching  for  compounds  already 
formed  and  existing  in  unknown  proportions  in  the  samples 
tested.  It  is  therefore  necessary  to  make  several  preparations 
of  each  sample,  in  order  that  we  may  obtain  the  widest  range 
of  possibihty  for  characteristic  crystalhzations.  The  following 
method  of  procedure  will  usually  give  satisfactory  results:  For 
a  dialyzer  use  a  fairly  wide  glass  tube,  over  one  end  of  which 
has  been  tightly  tied  a  piece  of  parchment  (Fig.  26),  or  better, 


PLATE   VIII.— ANALYSIS   OF   SALIVA. 


Fig.  I. 
Ammonium  Chloride. 


Fig.  3. 
A,  Magnesium  Lactate  (P.  L.). 
B,  Calcium  Lactate  (P.  L.). 


Fig.  2. 
Sodium  Chloride,  1%. 


Fig.  4. 
A,  Magnesium  Acid  Lactate. 
B,  Calcium  Acid  Lactate. 


Fig.  5. 
Potassium  Chlorid,  |%  Solution. 


f  IG.  6. 
Potassium  Chlorid,  |%  Solution. 


ANALYSIS  OF  SALIVA 


327 


a  small  dialyzing  tube  made  entirely  of  parchment.  Place 
about  15  c.c.  of  saliva  in  the  dialyzing  tube,  and  suspend  it  in 
a  small  beaker  or  wine-glass  which  contains  an  equal  volume  of 
distilled  water.  At  the  end  of  twenty-four  hours  the  distilled 
water  will  contain  the  dialyzable  salts  in  nearly  the  same  con- 
centration as  existed  in  the  original  saliva.  Take  four  previ- 
ously prepared  cell-sHdes  (microscope 
sHdes  on  which  a  ring  of  Bell's  or 
other  microscopical  cement  has  been 
placed)  and  fill  each  cell  full  of  the 
dialyzed  saliva.  Put  number  i  in  a 
warm  place  that  it  may  evaporate 
rapidly,  leave  number  2  exposed  to 
the  air  at  the  room  temperature  and 
it  will  dry  in  from  half  to  three- 
quarters  of  an  hour.  Place  number 
3  under  a  large  beaker,  or  small  bell- 
jar,  and  cover  number  4  with  a  cover- 
glass,  and  from  time  to  time  examine 

the  crystals  that  may  be  formed.  Numbers  3  and  4  will  prob- 
ably take  several  hours,  perhaps  several  days,  before  crystal- 
lization is  complete.  When  the  crystals  have  appeared,  the 
preparation  may  be  preserved  by  mounting  in  xylol  balsam. 
In  attempting  to  obtain  crystals  from  the  saKva  before  dialy- 
zation,  results  are  usually  unsatisfactory,  owing  to  the  presence  of 
mucin  and  other  organic  substances  which  interfere  with  the  crys- 
tallization. The  crystals  obtained  by  this  method  are  principally 
sodium  oxalate,  lactates,  and  acid  lactates  of  Ume  and  magnesia, 
and  rarely  urates  of  the  alkalis.  (For  forms  of  these  crystals  see 
Plate  VIII,  Figs.  3  and  4,  and  Plate  II,  Fig.  4,  pp.  327  and  162.) 


Fig.  26. 


Laboratory  Exercise  LXX. 

Exp.  214.     Action  of  Saliva  upon  Starch.  —  Take  some  fil- 
tered saliva  in  a  test-tube  and  place  in  the  water-bath  at  40°  C, 


328  DIGESTION 

for  five  or  ten  minutes.  Put  some  starch  paste  into  a  second 
test-tube  and  place  this  also  in  the  water-bath  for  a  while,  then 
mix  the  two  (lo  c.c.  of  starch  paste  to  3  c.c.  of  undiluted  sahva) 
and  return  to  the  water-bath.  The  starch  is  changed  first  to 
soluble  starch  (if  originally  a  thick  paste,  it  becomes  fluid  and 
loses  its  opalescence),  then  to  erythrodextrin,  which  gives  a 
red  color  with  iodin,  and  finally  to  achroodextrin,  which  gives 
no  reaction  with  iodin,  and  to  maltose.  Prove  these  changes 
as  follows:  Every  minute  or  two  take  out  a  drop  of  the  mix- 
ture, place  it  on  a  porcelain  plate,  and  add  a  drop  of  iodin  solu- 
tion. This  gives  first  a  blue  color,  showing  the  presence  of 
starch;  later  a  violet  color,  due  to  the  mixture  of  the  blue  of 
the  starch  reaction  with  the  red  caused  by  the  dextrin;  next  a 
reddish-brown  color,  due  to  erythrodextrin  alone  (starch  being 
absent),  and  finally  no  reaction  at  all  with  iodin,  proving  the 
absence  of  starch  and  erythrodextrin.  The  fluid  now  contains 
achroodextrin  and  maltose.  Test  for  the  latter  with  Fehling's 
solution  and  with  Barfoed's  reagent. 

Exp.  215.  Influence  of  Conditions  on  Ptyalin  and  its  Amylo- 
lytic  Action.  —  Report  and  explain  the  results  of  the  following 
experiments : 

{a)  Boil  a  few  cubic  centimeters  of  the  saliva,  then  add 
some  starch  paste,  and  place  in  the  water-bath  at  40°  C.  After 
five  minutes  test  for  sugar. 

(&)  Take  two  test-tubes:  put  some  starch  paste  in  one,  and 
saHva  in  the  other,  and  cool  them  to  0°  C,  in  a  freezing  mixture. 
Mix  the  two  solutions,  and  keep  the  mixture  surrounded  by 
ice  for  several  minutes,  then  test  a  portion  for  sugar.  Now 
place  the  remainder  in  the  water-bath  at  40°  C,  and  after  a 
time  test  for  sugar. 

(c)  Carefully  neutraHze  20  c.c.  of  saliva  with  very  dilute 
HCl  (the  0.2%  diluted),  and  dilute  the  whole  to  100  c.c.  Test 
the  action  of  this  neutrahzed  saliva  on  starch. 

{d)  To  5  c.c.  of  starch  paste  add  10  c.c.  of  0.2%  HCl  and 


ANALYSIS  OF  SALIVA  329 

5  c.c.  of  neutral  saliva,  and  expose  the  mixture  for  a  while  at 
40°  C,  and  test  for  sugar. 

(e)  To  5  c.c.  of  starch  paste  add  10  c.c.  of  a  0.5%  solution 
of  Na2C03  and  5  c.c.  of  neutral  saliva,  and  expose  the  mixture 
for  a  while  at  40°  C,  and  test  for  sugar. 

(/)  Carefully  neutralize  (d)  and  (e),  and  again  test  the  action 
of  the  two  on  starch. 

(g)  Mix  a  Httle  uncooked  starch  with  saHva,  expose  to  a 
temperature  of  40°  C.  for  a  while,  and  test  for  sugar. 

Exp.  216.  In  three  separate  test-tubes  place  a  few  cubic 
centimeters  of  dilute  solutions  of  KCNS  or  NH4CNS,  of  meconic 
acid,  and  of  acetic  acid ;  add  to  each  a  few  drops  of  ferric  chlorid, 
and  notice  that  a  similar  color  is  obtained  in  each  case.  Divide 
the  contents  of  each  tube  into  two  portions,  and  to  one  set  add 
HCl;  to  the  other  add  mercuric-chlorid  solution.  Formulate  a 
method  of  distinguishing  from  the  sulphocyanates,  meconates, 
and  acetates. 

Tests  for  Abnormal  Constituents. 

Acetone,  glycogen,  and  dextrin  have  already  been  con- 
sidered. Urea  may  be  demonstrated  as  follows:  To  a  given 
volume  of  saliva  add  twice  as  much  alcohol.  This  serves  to 
precipitate  proteins.  Filter  and  evaporate  on  a  water-bath  till 
original  volume  is  reached,  or  evaporate  to  less  than  original 
volume,  and  make  up  with  distilled  water.  Then  determine  urea 
with  Squibb's  apparatus,  as  used  for  urine,  except  that  in  this 
case  it  will  be  necessary  to  replace  the  2-c.c.  pipette  with  a  small 
burette,  and  introduce  10  c.c.  of  the  prepared  saliva.  Then  it  will 
be  necessary  to  allow  for  these  10  c.c.  by  subtracting  this  amount 
from  the  volume  of  water  received  in  the  graduated  cyhnder,  and 
the  remaining  number  of  cubic  centimeters,  multipHed  by  two, 
will  correspond  to  the  urea  in  20  c.c.  of  the  sample.  The  percent- 
age shown  on  the  card,  divided  by  ten,  will  give  the  per  cent  of 
urea  required.     See  also  method  by  Dr.  H.  C.  Ferris  on  page  320. 


330  DIGESTION 

Lactic,  butyric,  and  ucetic  acids  may  each  be  tested  for,  quali- 
tatively, by  the  methods  given  under  gastric  digestion  (q.  v.). 

Mercury.  —  A  very  dehcate  test  may  be  made  for  this  metal 
as  follows:  Collect  as  large  a  sample  of  saliva  as  possible,  dilute 
with  an  equal  volume  of  water,  acidify  with  a  few  drops  of 
HCl,  throw  in  a  few  very  small  pieces  of  copper- turnings,  which 
have  been  recently  cleaned  in  dilute  HNO3,  and  boil  for  at 
least  one-half  hour,  keeping  up  the  volume  by  occasional  addi- 
tions of  water.  Remove  the  copper-filings,  dry  thoroughly  on 
filter-paper,  and  place  in  a  large-sized  watch-glass  (3  inches). 
In  another  watch-glass  of  similar  size  place  one  drop  of  solu- 
tion of  gold  chlorid,  and  quickly  invert  so  that  the  drop  remains 
hanging  on  the  under  side  of  the  glass.  Now  place  this  watch- 
glass  directly  over  the  one  containing  the  copper,  so  that  the 
chlorid  of  gold  shall  be  suspended  directly  above  the  turnings 
and  perhaps  a  half  inch  from  them,  then  gently  heat  the  lower 
watch-glass  with  a  very  small  flame,  when  the  sHghtest  trace 
of  mercury,  which  may  have  been  deposited  upon  the  copper, 
will  be  volatilized,  reducing  the  chlorid  of  gold,  and  causing  a 
purpUsh  ring  to  appear  around  the  edge  of  the  drop.  If  no 
reduction  of  the  gold  occurs,  mercury  is  absent. 

Lead,  which  occasionally  occurs  in  saliva,  may  be  detected 
by  the  methods  given  under  urine. 

Microscopical  examination  of  the  sediment  should  be  made 
in  every  instance.  Normal  saliva  will  contain  epitheHum  from 
various  parts  of  the  oral  cavity,  an  occasional  leucocyte,  and 
occasional  mold  fungi,  leptothrix,  etc.  Constituents,  which  per- 
haps are  not  properly  classed  as  normal  and  at  the  same  time 
are  not  pathological,  are  fat  globules,  a  rare  blood-corpuscle, 
sarcinse,  extraneous  material  as  food  particles,  starch  granules, 
muscle  fibers,  etc.  An  excessive  amount  of  blood,  fat,  pus,  or 
micro-organisms  would,  of  course,  indicate  pathogenic  conditions. 
The  bacteriological  investigation  of  samples  of  saliva  is  always 
of  interest,  and  may  be  necessary,  but  the  detailed  methods  of 
such  investigation  do  not  lie  within  the  scope  of  this  work. 


CHAPTER  XXXV. 
GASTRIC   DIGESTION. 

Digestion  begins  with  the  action  of  the  saliva  upon  the 
carbohydrates,  and  if  mastication  is  sufficiently  prolonged,  the 
ptyaHn  may  convert  an  appreciable  quantity  of  starchy  food 
into  a  more  soluble  form  before  it  reaches  the  stomach.  In  the 
stomach  the  amylolitic  action  of  the  saliva  is  stopped  by  the 
contact  with  the  gastric  juice.  A  certain  amount,  however,  of 
saHvary  digestion  takes  place  within  the  stomach,  due  to  the 
fact  that  considerable  time  necessarily  elapses  before  the  acid 
of  the  gastric  juice  has  been  secreted  in  sufficient  quantity  to 
completely  permeate  and  acidify  the  mass  of  food  received 
from  the  oesophagus.  As  has  been  previously  shown,  a  very 
feeble  degree  of  acidity  is  conducive  to  the  activity  of  the 
amylolytic  ferment.  The  average  alkahnity  of  the  saHva,  cal- 
culated as  Na2C03,  is  about  0.15  of  1%. 

The  first  step  in  the  gastric  digestion  is  probably  the  union 
of  the  stomach  HCl  with  the  proteins,  forming  acid  albumins 
(metaproteins)  or  alhed  bodies  which  are  changed  by  pepsin, 
which  is  the  active  digestive  ferment  of  the  stomach,  into  the 
albumoses  (proteoses),  and  sHght  amounts  of  the  various  pep- 
tones, following  practically  the  changes  produced  experimentally 
on  page  332. 

Pepsin  is  an  active  proteolytic  enzyme  occurring  in  the  cells 
of  the  stomach-wall  as  pepsinogen,  which  is  decomposed  by 
the  HCl  with  the  formation  of  free  pepsin.  Pepsin  works  only 
in  faintly  acid  solutions,  and  in  the  stomach  carries  the  diges- 
tion of  proteins  but  little  beyond  the  stage  of  the  proteoses. 

Hydrochloric  acid  is  obtained  from  the  fundus  glands  by  an 


332  DIGESTION 

interchange  of  radicles  between  alkaline  chlorids  and  the  car- 
bonates of  the  blood.*  The  quantity  present  varies  from  o  to 
3/10  per  cent,  0.18%  being  about  the  most  favorable  for  peptic 
activity.  Aside  from  HCl,  various  organic  acids  may  be  pres- 
ent in  the  stomach  contents ;  lactic  acid,  butyric  acid,  and  acetic 
acid  are  the  most  important  of  this  class,  tests  for  which  are 
referred  to  under  analysis  of  gastric  contents. 

Hydrochloric  acid  combines  with  protein  substances  of  the 
food,  forming  a  rather  unstable  compound  in  which  condition 
the  acid  is  known  as  combined  hydrochloric  acid  in  distinction 
from  the  free  hydrochloric  acid  which  the  gastric  juice  may  also 
contain.  The  combined  HCl  possesses  only  in  modified  form 
the  properties  of  free  HCl,  and  hence  is  less  liable  to  stop  the 
digestive  action  of  ptyalin  from  the  saliva. 

Rennin  is  a  second  enzyme  found  in  the  stomach.  This,  like 
pepsin,  also  exists  as  a  zymogen,  and  is  liberated  or  developed 
by  the  presence  of  acid.  Its  action  is  particularly  the  curdling 
of  milk,  i.e.,  the  decomposition  of  caseinogen  (Exp.  222),  and 
consequent  coagulation  of  the  casein.  A  third  enzyme,  existing 
in  the  stomach  in  very  small  quantities,  is  a  gastric  lipase,  or 
stomach  steapsin,  a  fat-splitting  enzyme,  the  action  of  which 
is  comparatively  weak  and  of  but  slight  importance. 


Laboeatory  Exercise  LXXI. 

Analysis  of  Gastric  Contents  and  Experiments  with  Pepsin. 

The  following  solutions  will  be  found  in  the  laboratory: 

A.  A  0.2%  Solution  of  HCl.  — ■  This  is  prepared  by  diluting 
6.5  c.c.  of  concentrated  HCl  (sp.  gr.  1.19)  with  distilled  water 
to  I  liter. 

B.  A  Solution  of  Pepsin.  —  Prepared  by  dissolving  two 
grams  of  pepsin  in  1000  c.c.  of  water. 

*  Long's  Physiological  Chemistry. 


GASTRIC  DIGESTION  333 

C.  A  Pepsin-hydrocMoric-acid  Solution.  —  Prepared  by  dis- 
solving two  grams  of  pepsin  in  1000  c.c.  of  solution  A. 

Or,  add  to  150  c.c.  of  solution  A  about  10  c.c.  of  the  glyc- 
erol extract  of  the  mucous  membrane  of  the  stomach. 

Exp.  217.  Take  five  test-tubes  and  label  a,  b,  c,  d,  e.  Fill 
as  indicated  below.  Place  in  a  water-bath  at  40°  C,  and 
examine  an  hour  later,  and  again  the  next  day. 

(a)  3  c.c.  pepsin  solution  -1-  10  c.c.  water  +  a  few  shreds  of 
fibrin. 

(&)   10  c.c.  0.2%  HCl  -|-  a  few  shreds  of  fibrin. 

(c)  3  c.c.  pepsin  solution  +  10  c.c.  0.2%  HCl,  and  a  few 
shreds  of  fibrin. 

{d)  3  c.c.  pepsin  solution  -f  10  c.c.  0.2%  HCl,  boil,  and  then 
add  a  few  shreds  of  fibrin. 

(e)  3  c.c.  pepsin  solution  -f  10  c.c.  0.2%  HCl,  and  a  few 
shreds  of  fibrin  which  have  been  tied  firmly  together  into  a 
ball  with  a  thread. 

Make  a  note  of  all  changes. 

Exp.  218.  Filter  c.  Neutralize  with  dilute  Na2C03.  Filter 
again.     Why?     Test  the  filtrate  for  the  biuret  reaction. 

Exp.  219.  To  5  grams  fibrin  add  30  c.c.  of  the  pepsin  solu- 
tion and  100  c.c.  0.2%  HCl.  Set  in  the  water-bath  at  40°  C, 
stirring  frequently,  and  leave  in  the  water-bath  overnight. 
Observe  the  undigested  residue,  on  the  following  day,  and  also 
a  slight  flocculent  precipitate.     What  is  this  precipitate? 

Filter  and  carefully  neutralize  the  filtrate.  A  precipitate 
varying  with  the  progress  of  the  digestion  will  form.  What 
is  it? 

Remove  this  by  filtration,  and  saturate  this  filtrate  with 
(NH4)2S04.  Filter.  Save  precipitate  and  filtrate.  Of  what 
does  each  consist? 

Exp.  220.  Dissolve  the  last  precipitate  of  Exp.  219  in  water, 
and  try  the  following  tests: 

(a)  Biuret  reaction. 


334  DIGESTION 

(b)  Effect  of  boiling. 

(c)  Test  with  NHO3,  as  in  performing  test  for  albumin  in  the 
urine,  page  359. 

Exp.  221.  To  the  last  filtrate  of  Exp.  219  add  an  equal  vol- 
ume of  95%  alcohol,  and  stir  thoroughly.  The  peptones  will 
collect  in  a  gummy  mass  about  the   stirring-rod. 

(a)  Determine  the  solubility  of  peptones  in  water. 

(b)  What  is  the  effect  of  heat  when  so  dissolved  ? 

(c)  Try  the  biuret  reaction. 

Exp.  222.  Demonstration  of  the  Rennet  Enzyme.  —  Place 
10  c.c.  of  milk  in  each  of  three  test-tubes.  Label  the  test-tubes 
I,  2,  3. 

To  I  add  a  drop  of  neutralized  glycerol  extract  of  the 
mucous  membrane  of  the  stomach  (made  from  the  stomach  of 
the  calf). 

To  2  add  a  drop  of  neutrahzed  glycerol  extract,  and  boil 
at  once. 

To  3  add  a  few  cubic  centimeters  of  (NH4)2C204  solution, 
and  then  a  drop  of  a  glycerol  extract. 

Place  these  tubes  in  the  water-bath  at  40°  C,  and  examine 
after  five  to  ten  minutes.     Explain  results  in  each  case. 

Continue  heating  tube  3  for  half  an  hour,  then  add  2  or  3 
drops  CaCU  solution.     The  Hquid  instantly  soHdifies.     Why? 

Exp.  223.  Digestion  of  Casein.  —  Determine  the  products  of 
the  digestion  of  the  curd  from  the  last  experiment. 

Exp.  224.  Tests  for  Free  Hydrochloric  Acid. — Try  each 
of  the  following  tests  with  (a)  HCl  (0.2%,  0.05%,  and  0.01% 
successively);  (b)  lactic  acid  (1%);  (c)  mixtures  containing 
equal  volumes  of  (a)  and  (b).     Tabulate  the  results. 

(a)  Dimethylaminoazobenzene.  —  Use  one  or  two  drops  of  a 
0.5%  alcohoHc  solution.  In  the  presence  of  free  mineral  acids 
a  carmine-red  color  is  obtained. 

{b)  Gunzburg's  Reagent.  —  Phloroglucin,  2  grams;  vanillin, 
I  gram;  alcohol,  100  c.c.     Place  two  or  three  drops  of  the  solu- 


GASTRIC  DIGESTION  335 

tion  to  be  tested  in  a  porcelain  dish,  add  one  or  two  drops  of 
the  reagent,  and  evaporate  on  a  water-bath.  In  the  presence 
of  free  hydrochloric  acid  a  rose-red  color  develops. 

(c)  Boas^  Reagent.  —  This  is  prepared  by  dissolving  5  grams 
of  resublimed  resorcinol  and  a  gram  of  cane-sugar  in  100  grams 
of  94%  alcohol.  Take  three  or  four  drops  each  of  the  reagent 
and  the  solution  to  be  tested,  and  cautiously  evaporate  to 
dryness.  In  the  presence  of  a  free  mineral  acid  a  rose  or  Ver- 
million red  color  is  obtained.     This  gradually  fades  on  cooling. 

(d)  TropcBolin  00.  —  Use  one  or  two  drops  of  a  saturated 
alcoholic  solution. 

{e)  Congo-red.  —  Use  filter-paper  which  has  been  dipped  into 
a  solution  of  the  reagent  and  then  dried. 

Exp.  225.  To  5  c.c.  egg-albumin  in  solution  add  i  c.c.  of 
0.2%  HCl.  Mix  thoroughly,  and  test  for  the  presence  of  free 
HCl.  What  is  the  result?  How  do  you  explain  it?  Repeat 
the  test,  using  a  solution  of  peptone  in  place  of  the  egg-albumin. 

Exp.  226.  Tests  for  Lactic  Acid.  —  Uffelmann's  reagent. 
Mix  10  c.c.  of  a  4%  solution  of  carbolic  acid  with  20  c.c.  of 
water,  and  add  a  drop  or  two  of  ferric  chlorid. 

To  5  c.c.  of  the  reagent  add  a  few  drops  of  the  lactic-acid 
solution.     Note  the  canary-yellow  color. 

Does  the  presence  of  free  HCl  interfere  with  this  reaction  ? 

A  more  delicate  reagent  is  obtained  by  adding  three  or  four 
drops  of  a  10%  ferric-chlorid  solution  to  50  c.c.  of  water.  Such 
a  solution  has  a  very  faint  yellow  color,  which  is  distinctly  in- 
tensified by  lactic  acid. 

Using  5  c.c.  of  this  nearly  colorless  solution  for  each  experi- 
ment, note  the  effect  of  (a)  0.2%  HCl;  {h)  acid  phosphate  of 
sodium;  (c)  alcohol;  {d)  glucose;  (e)  cane-sugar.  What  con- 
clusions do  you  reach  concerning  the  value  of  this  test,  when 
applied  directly  to  the  gastric  contents? 

The  test  is  best  applied  to  an  aqueous  solution  of  the  ethereal 
extract  of  the  gastric  contents.     Add  to  the  contents  two  drops 


336  DIGESTION 

of  HCl,  boil  to  a  syrup,  and  extract  with  ether.  Dissolve  the 
residue  obtained  upon  evaporation  of  the  ether  in  a  little  water, 
and  test  for  lactic  acid. 

Exp.  227.  Test  for  butyric  acid;  see  ethyl  butyrate,  page 
207. 

Exp.  228.     Test  for  acetic  acid;   see  acetates  (page  94). 

Exp.  229.  The  acidity  of  the  gastric  contents  may  be  deter- 
mined as  follows:  To  5  c.c.  of  the  filtered  contents,  diluted  with 
25  to  30  c.c.  of  water  in  an  Erlenmeyer  flask,  add  2  or  3  drops 
of  a  solution  of  dimethylaminoazobenzene.  Titrate  with  N/io 
alkali  till  the  color  changes  to  a  yellow  which  fairly  matches 
the  indicator;  this  represents  the  free  HCl.  To  this  mixture 
add  a  few  drops  of  phenolphthalein  solution,  and  continue  the 
titration  until  a  permanent  pink  color  is  obtained.  The  N/io 
alkali  used  will  represent  the  total  acidity,  combined  HCl  and 
organic  acids.  The  organic  acids  will  not  be  present  in  gastric 
contents  in  the  presence  of  any  appreciable  amount  of  free 
HCl,  as  they  are  derived  almost  entirely  from  fermentations 
which  are  inhibited  by  the  hydrochloric  acid. 


CHAPTER  XXXVI. 
PANCREATIC  DIGESTION  AND   BILE. 

It  may  be  an  aid,  in  remembering  the  various  digestive  fer- 
ments, to  note  that  in  the  sahva  we  have  one  principal  ferment, 
ptyalin;  in  the  stomach  we  have  two  principal  ferments,  pepsin 
and  rennin;  in  the  pancreatic  juice,  three  active  ferments.  The 
first  is  a  proteolytic  enzyme,  known  as  trypsin^  which  continues 
the  work  of  the  gastric  juice,  and  converts  the  proteoses  into 
peptones,  tyrosin,  leucin,  etc. 

Trypsin  is  the  proteolytic  enzyme  of  the  pancreatic  juice. 
It  is  a  much  more  energetic  digestive  agent  than  the  pepsin 
found  in  the  stomach,  but  it  differs  in  that  it  acts  in  an  alkaline 
media  rather  than  an  acid.  Trypsin  exists,  l&e  other  proteo- 
lytic enzymes,  as  a  parent  enzyme,  trypsinogen,  which  in  itself 
is  not  a  digestive  ferment,  but  which  is  rendered  active  (acti- 
vated) by  another  substance  known  as  enterokinase. 

The  enterokinase  occurs  in  the  intestinal  juice,  and  seems  to 
be  secreted  only  as  it  is  needed  for  the  activation  of  the  tryp- 
sinogen. Enterokinase  does  not  in  itself  possess  digestive 
power,  but  its  action  is  destroyed  by  heat  and  in  this  it  resembles 
the  enz3rmes. 

Amylopsin  is  the  starch  digesting  enzyme  of  the  pancreatic 
juice.  Here,  again,  we  have  an  enzyme  much  more  energetic 
in  its  action  upon  carbohydrates  than  'the  ptyalin  of  the  saliva. 
It  converts  starch  into  maltose  and  to  some  extent  to  dextrin. 
The  amylopsin  is  active  in  faintly  alkahne  or  very  faintly  acid 
solution;  more  acid,  however,  retards  its  action. 

Steapsin  is  the  fat-splitting  enzyme  of  the  pancreatic  juice. 
It  spHts  the  fat,  as  indicated  on  page  209,  into  glycerol  and 

337 


338  DIGESTION 

fatty  acids,  and  also  acts  as  an  emulsifying  agent.  The  free 
fatty  acids  thus  formed  unite  with  the  alkaHne  bases  found  in 
the  intestines  to  form  soaps,  which  are  also  active  emulsifying 
agents. 

The  pancreatic  juice  and  the  bile  enter  the  duodenum  in 
very  close  proximity,  and  the  digestive  action  of  each  is  depen- 
dent, to  a  considerable  extent,  upon  the  presence  of  the  other. 

Bile.  —  A  secretion  produced  by  the  liver  and  stored  in  the 
gall-bladder,  from  which  it  is  delivered  to  the  intestines,  where 
it  aids  materially  in  emulsification  and  absorption  of  the  fats. 

Composition  of  Bile.  —  Its  composition  is  very  complex, 
but  there  are  two  acids  and  two  coloring  matters  which  are  of 
particular  importance,  and  derivatives  of  which  indicate  the 
presence  of  bile  in  saliva,  urine,  blood,  etc.  The  acids  are 
taurocholic  and  glycocholic,  existing  principally  as  sodium  or 
potassium  salts.  The  coloring  matters  are  bilirubin  and  bili- 
verdin;  the  former  predominates  in  human  bile  and  the  latter 
in  ox  bile.  Glycocholic  acid  upon  hydrolysis  splits  into  a 
simpler  acid  (cholalic)  and  glycocoll,  glycocoll  being  an  amino- 
acetic  acid  (page  222),  which  is  undoubtedly  an  antecedent  of 
urea.  Both  of  the  bile-pigments  are  derived  from  the  coloring 
matter  of  the  blood.  The  appearance  of  either  of  these  or  of 
their  derivatives,  in  either  urine  or  saliva,  is  indicative  of  patho- 
logical conditions  either  of  the  liver-  or  bile-ducts,  causing  ob- 
struction to  the  outflow  of  the  bile  or  a  destruction  of  the  red- 
blood  corpuscles.*  The  blood  pigments,  according  to  Michaels, 
are  easily  demonstrable  in  the  desiccated  saliva  by  means  of 
polarized  light. 

The  intestinal  juice  contains  a  number  of  substances  play- 
ing an  important  part  in  the  preparation  of  food  material  for 
assimilation.  Among  them  is  erepsin  (erepase).  This  is  a 
protein-splitting  enzyme  acting  upon  the  products  of  tryptic 
digestion.     It  has  Httle  power  upon  the  simple  proteins,  but  will 

*  Ogden. 


PANCREATIC  DIGESTION  AND  BILE  339 

split  the  peptones  into  amino  acids.  There  are  also  in  the 
intestinal  juice  certain  amylolytic  enzymes  which  continue 
the  digestive  action  started  byamylopsin  or  by  ptyaUn  of  the 
sahva. 

Secretin,  excreted  by  the  mucous  membrane  of  the  intestine, 
is  a  substance  differing  materially  from  the  digestive  ferments 
in  that  it  is  not  destroyed  by  heat.  It  acts  not  as  an  activator 
in  the  sense  that  it  starts  specific  chemical  action,  but  as  an 
essential  constituent  for  the  secretion  of  the  various  digestive 
flmds;  i.e.,  the  secretin  in  the  blood  starts  the  flow  of  pancre- 
atic juice,  for  instance,  which  contains  the  parent  enzyme,  tryp- 
sinogen,  which  in  turn  requires  the  action  of  enterokinase  before 
it  is  in  condition  to  perform  its  digestive  action.  Some  authori- 
ties claim  that  the  secretin  itself  exists  as  a  pro-secretin,  from 
which  it  is  liberated  by  action  of  acid. 

Laboratory  Exercise  LXXII. 
Experiments  with  Pancreatic  Juice. 

Exp.  230.  Proteolytic  Action.  — To  25  c.c.  of  a  1%  solution 
of  Na2C03  add  a  few  drops  of  the  pancreatic  extract.  Place 
some  pieces  of  fibrin  in  this  liquid,  and  keep  in  the  water-bath 
at  40°  C.  till  the  fibrin  has  disappeared  (one  or  two  hours  prob- 
ably). Observe  the  digestion  from  time  to  time.  Note  that 
the  fibrin  does  not  swell  and  dissolve  as  in  gastric  digestion,  but 
that  it  is  eaten  away  from  the  edges. 

Filter.  What  is  the  precipitate?  Carefully  neutraHze  the 
filtrate  with  0.2%  HCl.  Another  precipitate  may  appear. 
What  is  this? 

Again  filter,  if  necessary,  and  test  the  filtrate  for  proteoses 
and  peptones  as  directed  under  gastric  digestion. 

Exp.  231.  Formation  of  Leucin  and  Tyrosin.  —  Perform  a 
similar  experiment,  using  boiled  fibrin  and  adding  a  few  drops 
of  a  20%  solution  of  thymol,  or  a  few  drops  of  chloroform  water. 


340  DIGESTION 

Why  use  boiled  fibrin,  and  why  add  thymol  or  chloroform? 
Digest  for  forty-eight  hours,  and  then  examine  as  follows: 
Filter,  neutraHze,  and  concentrate  by  evaporation  on  the  water- 
bath.  Crystals  of  tyrosin  (and  possibly  leucin)  usually  sepa- 
rate.    Examine  microscopically. 

Exp.  232.  Amylolytic  Action.  —  To  some  starch  paste  in  a 
test-tube  add  a  drop  or  two  of  the  pancreatic  extract  and  place 
in  the  water-bath  at  40°  C.  After  a  few  minutes  test  for  sugar 
and  report  the  result. 

Exp.  233.  The  Piolytic  {Fat-splitting)  Action.  —  For  the 
demonstration  of  this  action  use  natural  pancreatic  juice,  or 
finely  divided  fresh  pancreas,  or  a  recently  prepared  extract. 

To  some  perfectly  neutral  olive-oil,  colored  faintly  blue 
with  litmus,  add  half  its  volume  of  the  pancreatic  extract, 
shake  thoroughly,  and  keep  at  40°  C.  for  twenty  minutes. 
Record  the  result.     Reserve  for  next  experiment. 

Exp.  234.  Emulsifying  Action.  —  To  10  c.c.  of  a  0.2%  solu- 
tion of  Na2C03  add  a  few  drops  of  the  mixture  used  in  Exp.  233. 
Shake  thoroughly,  and  report  the  result.  Referring  to  the 
earlier  experiments  on  emulsification  (see  Fats),  explain  the 
efficacy  of  the  pancreatic  juice  in  emulsifying  fats. 


Laboratory  Exercise  LXXIIL 
Experiments  with  Bile. 

Exp.  235.  Color.  —  Note  the  difference  in  color  between 
human  bile  and  ox  bile.     Explain. 

Exp.  236.  Reaction.  —  Dilute  some  bile  with  four  parts  of 
water.  Immerse  a  strip  of  red  litmus-paper,  then  remove  and 
wash  with  water.     Note  the  reaction. 

Exp.  237.  Nucleo-albumin.  —  Dilute  bile  with  twice  its 
volume  of  water,  filter  if  necessary,  and  add  acetic  acid.  What  is 
the  precipitate?    How  distinguished  from  mucin? 


PANCREATIC   DIGESTION  AND  BILE  341 

Exp.  238.  Filter  237  and  test  the  filtrate  for  proteins. 
Report  the  result. 

Exp.  239.  Separation  of  Bile  Salts.  —  Mix  20  c.c.  of  bile 
with  animal  charcoal  to  form  a  thick  paste,  and  evaporate  on  the 
water-bath  to  complete  dryness.  Pulverize  the  residue  in  a 
mortar,  transfer  to  a  flask,  add  25  c.c.  of  absolute  alcohol,  and 
heat  on  the  water-bath  for  half  an  hour.  Filter.  To  the  fil- 
trate add  ether  till  a  permanent  precipitate  forms.  Let  the 
mixture  stand  for  a  day  or  two,  and  then  filter  off  the  crystalline 
deposit  of  bile  salts.  Save  the  filtrate  which  contains  choles- 
terin.     (Plate  VII,  Fig.  4,  page  296.) 

Exp.  240.  Bile-pigments.  —  (a)  Gmelin's  Test.  —  Take  some 
bile  in  a  wine-glass  and  underlay  with  yellow  HNO3,  in  the 
manner  described  in  testing  saliva  for  albumin.  Notice  the 
play  of  colors,  beginning  with  green  and  passing  through  blue, 
violet,  and  red  to  yellow,  at  the  jimction  of  the  two  liquids. 
Explain. 

(&)  lodin  Test.  —  Place  10  c.c.  of  dilute  bile  in  a  test-tube, 
and  add  slowly  two  or  three  cubic  centimeters  of  dilute  tincture 
of  iodin,  so  that  it  forms  an  upper  layer.  A  bright  green  ring 
forms  at  the  line  of  contact. 

Exp.  241.  Cholesterin.  —  Examine  under  the  microscope  the 
crystals  obtained  by  the  cautious  evaporation  of  the  alcohol- 
ether  filtrate  of  Exp.  239.  For  color  reactions  refer  to  demon- 
strations. 

Exp.  242.  Action  of  Bile  in  Digestion.  —  (a)  Take  three 
test-tubes.  In  one  mix  10  c.c.  of  bile  and  2  c.c.  of  neutral  olive- 
oil;  in  the  second,  10  c.c.  of  bile  and  2  c.c.  of  rancid  oUve-oil; 
in  the  third,  10  c.c.  of  water  and  2  c.c.  of  neutral  oil.  Shake  and 
place  in  a  water-bath  at  40°  C.  for  some  time.  Note  the  extent 
and  the  permanency  of  the  emulsion  in  each  case. 

(&)  Into  each  of  two  funnels  fit  a  filter-paper.  Moisten  one 
with  water  and  the  other  with  bile,  and  into  each  pour  an  equal 
volume  of  olive-oil.     Set  aside  for  twelve  hours  (with  a  beaker 


342  DIGESTION 

under  each  funnel).     Do  you  notice  any  dijEference  in  the  rate 
of  filtration? 

(c)  Add  drop  by  drop  a  solution  of  bile  salts  to  {a)  a  solution 
of  egg-albumin;  {b)  a  solution  of  acid-albumin;  (c)  a  solution 
obtained  by  digesting  a  bit  of  fibrin  in  gastric  juice  and  filtering. 
Explain  the  results. 


PART   VIII. 

URINE. 


CHAPTER  XXXVII. 
PHYSICAL   PROPERTIES   OF   URINE. 

Urine  is  a  solution  of  waste  products  from  the  blood.  It 
contains,  normally,  certain  coloring  matter,  urea,  uric  acid  in 
combination  with  alkaHne  bases,  various  organic  constituents 
in  slight  amounts,  including,  perhaps,  albumin  and  sugar, 
chlorid  of  sodium,  sulphates  and  phosphates  of  the  alkahs  and 
the  alkaline  earths.  Abnormally  the  urine  may  contain  albumin, 
sugar,  uric  acid  as  such,  bile,  salts  of  the  heavy  metals,  lead, 
mercury,  and  arsenic;  occasionally  albumose,  peptones,  lac- 
tates, acid  lactates,  oxalates,  carbonates,  hippuric  acid,  also 
organic  compounds,  resulting  from  insufficient  or  imperfect 
oxidations,  as  amino-acids,  leucin,  tyrosin,  and  acetone  bodies. 

We  are  to  study  the  urine,  not  primarily  with  a  view  to  the 
diagnosis  of  renal  disease,  which  is  more  particularly  the  prov- 
ince of  the  physician,  but  to  detect  irregularities  or  deficiencies 
in  the  body  metaboKsm,  and,  as  far  as  possible,  we  are  to  study 
the  methods  whereby  we  may  correct  and  regulate  the  mal- 
nutrition which  lies  at  the  foundation  of  many  diseases  of  the 
oral  cavity.  As  has  been  previously  stated  by  the  author,* 
if  there  are  diseases  of  the  oral  cavity  which  may  have  their 
etiology  in  some  systemic  derangement  not  easily  apparent, 
and  if  such  diseases  are  to  receive  the  attention  of  the  dentist, 
he  should  obtain  all  possible  light  on  every  case,  and  at  present 

*  International  Dental  Journal,  January,  1905. 
343 


344  URINE 

a  quantitative  analysis  of  the  urine  is  of  greater  value  than 
any  other  laboratory  aid.  In  examining  a  sample  of  urine  to 
obtain  information  as  above  indicated,  it  is  essential  that  the 
sample  be  a  portion  of  the  mixed  twenty-four-hour  quantity, 
and  that  the  total  amount  of  the  twenty-four-hour  excretion 
be  known.  In  collecting  samples  for  such  analysis  a  conven- 
ient method  is  to .  give  the  patient  a  one-  or  two-dram  vial, 
nearly  filled  with  water,  and  containing  three  or  four  drops  of  a 
commercial  formaldehyd  solution,  with  instructions  to  empty 
this  into  the  bottle,  or  other  receptacle,  in  which  the  twenty- 
four-hour  sample  is  collected.  Formaldehyd  if  used  in  this 
amount  has  no  effect  on  the  subsequent  analysis  and  is  a  sufficient 
preservative. 

Physical  Properties. 

Quantity.  —  The  quantity  of  urine  passed  in  twenty-four 
hours  normally  is  about  1200  to  1400  c.c.  for  an  adult  female 
and  100  or  200  c.c.  more  than  this  for  the  male.  The  amount 
is  increased  in  Bright's  disease,  in  diabetes,  and  various  other 
pathological  conditions,  also  in  cold  weather  when  less  mois- 
ture is  given  off  from  the  skin.  Normally,  the  quantity  passed 
during  twelve  day  hours,  as  8  a.m.  to  8  p.m.,  will  exceed  the 
amount  overnight  from  8  p.m.  to  8  a.m.  In  cases  of  chronic 
interstitial  nephritis  the  twelve-hour  night  quantity  exceeds  the 
day,  hence  it  is  desirable  in  collecting  a  twenty-four-hour  sample 
to  divide  the  time  as  suggested,  and  measure  the  amounts 
separately,  especially  if  there  is  any  suspicion  of  any  chronic 
kidney  disease.  A  diminished  quantity  of  urine  may  indicate 
simply  a  diminished  amount  of  water  taken  into  the  system. 
The  urine  is  diminished  pathologically  in  acute  conditions,  such 
as  fevers,  etc.,  but  such  samples  rarely  reach  the  dental  prac- 
titioner. 

Color.  —  The  normal  color  of  the  urine  is  usually  given  as 
straw  color  or  pale  yellow.  If  lighter  than  this  the  color  is 
regarded  as  pale,  if  darker  than  normal  it  is  regarded  as  high. 


PHYSICAL  PROPERTIES  OF    URINE  345 

The  urine  may  also  be  colored  by  various  abnormal  constitu- 
ents; it  may  be  bright  red  from  the  presence  of  blood,  or  choco- 
late colored  with  a  so-called  coffee-ground  sediment  from  de- 
composed-blood coloring  matter.  It  may  be  brown  to  yellow, 
bright  blue  or  green,  due  to  the  ingestion  of  various  drugs. 
If  bile  is  present  in  any  quantity  in  the  urine  it  will  have  a 
dark  or  smoky  appearance,  and,  upon  shaking,  the  foam  will 
have  a  distinctly  yellowish  or  yellowish-green  tint. 

Appearance.  —  In  addition  to  the  colors  mentioned  above 
urine  may  sometimes  have  a  smoky  appearance,  due  to  the 
presence  of  hematoporphyrin  or  iron-free  hematin,  often  found 
in  cases  of  lead-poisoning.  It  may  have  a  milky  appearance, 
due  to  presence  of  finely  divided  fat  globules,  as  in  chylous 
urine,  due  to  parasitic  disease  of  the  blood.  It  may  be  cloudy 
from  four  principal  causes:  first,  amorphous  urates;  second, 
amorphous  phosphates;  third,  pus;  and  fourth,  bacteria. 
These  may  easily  be  distinguished.  The  application  of  a  slight 
degree  of  heat  (insufficient  to  cause  coagulation  of  albumin) 
will  redissolve  the  urates,  and  clear  a  urine  which  is  cloudy 
from  this  cause.  A  deposit  of  phosphates  is  increased  by  the 
apphcation  of  heat,  but  clears  easily  upon  the  addition  of  a 
few  drops  of  acetic  acid.  A  urine  cloudy  from  the  presence 
of  pus  is  not  cleared  by  either  of  these  methods,  but  the  cloud 
settles  with  comparative  rapidity  and  pus  corpuscles  are  easily 
recognized  by  microscopical  examination  of  the  sediment.  If 
bacteria  are  present  in  sufficient  quantity  to  cause  cloudiness, 
the  sample  is  apt  to  be  alkaline  in  reaction  and  will  not  clear 
upon  ffitering.  If  it  is  necessary  to  obtain  a  clear  solution,  a 
little  magnesium  mixture  may  be  added  to  the  urine,  then  a 
little  sodium  phosphate;  warm  gently  with  agitation,  when 
the  precipitated  ammonium  magnesium  phosphate  will  me- 
chanically carry  down  the  bacteria,  and  a  ffitrate  may  be  ob- 
tained which,  after  acidifying  with  dilute  acetic  acid,  will  be 
suitable  for  an  albumin  test. 


346 


URINE 


Fig.  27. 


Specific  Gravity.  —  The  gravity  is  most  conveniently  taken 
with  a  urinometer  (Fig.  27).  Care  should  be  taken  in  the  selec- 
tion of  this  instrument  so  that  the  scale  graduation  may  be  accu- 
rate. The  fact  that  the  instrument  will  sink  in  distilled  water 
at  the  proper  temperature  (usually  60°  F.,  15^° 
C.)  to  the  o  mark,  is  not  a  sufficient  proof  of  its 
accuracy,  as  many  cheap  instruments  will  do 
this,  and  give  erroneous  readings  at  the  higher 
markings  of  the  scale.  Distilled  water  is  rep- 
resented by  1000,  and  the  relative  increase  in 
the  comparative  gravity  of  urines  will  be  easily 
represented  on  the  scale  ranging  from  1000  to 
1050.  As  the  first  two  figures  of  the  specific 
gravity  are  always  the  same  (10),  they  are 
usually  omitted  from  the  scale  which  is  made 
to  read  from  o  to  50  or  60.  The  reading  should 
be  made,  if  possible,  from  underneath  the  surface  of  the  Hquid,  as 
the  Hquid  is  usually  drawn  around  the  stem  by  adhesion,  so  that 
accurate  readings  from  the  surface  are  difficult.  The  specific 
gravity  of  normal  urine  is  from  1018  to  1022;  it  decreases  in 
cases  where  the  quantity  is  much  above  the  normal  (polyurias), 
unless  sugar  is  present.  It  is  increased  by  the  presence  of  sugar 
or  by  concentration,  whereby  the  normal  soKds  are  relatively 
increased.  In  case  the  quantity  of  urine  is  too  small  for  the 
determination  of  the  gravity  in  the  usual  way,  the  urinopyk- 
nometer,  devised  and  recommended  by  Dr.  Saxe  in  his  "Examina- 
tion of  the  Urine, "  may  be  employed.  See  page  317,  on  specific 
gravity  of  saliva. 

Reaction.  —  The  reaction  of  urine  is  normally  acid  to  litmus- 
paper,  due  to  the  presence  of  acid  sodium  phosphate.  The 
degree  of  acidity  is  roughly  indicated  by  the  intensity  of  color 
produced  with  the  carefully  prepared  litmus-paper.  More  ac- 
curate results  may  be  obtained  by  a  regular  volumetric  exam- 
ination (with  N/20  alkali),  or  by  the  test  for  urinary  acidities 


PHYSICAL  PROPERTIES  OF    URINE  347 

given    by    Freund    and    Topfer    who    suggest    the    following 
method : 

"To  10  c.c.  of  the  urine  add  two  to  four  drops  of  a  1%  solu- 
tion of  alizarin.  If  the  resulting  color  is  pure  yellow,  free  acids 
are  present;  if  deep  violet,  combined  acid  salts.  If  none  of 
these  colors  appear,  there  are  present  acid  salts  of  the  type 
of  disodic  phosphate.  The  amount  of  one-tenth  normal  HCl 
standard  solution  required  to  produce  a  pure  yellow  color  repre- 
sents the  alkaline  salts,  while  the  amount  of  one-tenth  normal 
sodium  hydrate  required  to  cause  a  deep  violet  represents  the 
acid  salts." 


CHAPTER  XXXVIII. 

NORMAL  CONSTITUENTS    OF   URINE. 

The  more  important  normal  constituents  of  the  urine  are 
urea,  uric  acid  (combined  as  urates),  chlorids,  phosphates, 
sulphates,  indoxyl,  coloring  matters;  traces  of  mucin,  organic 
acids,  carbonates,  hippuric  acid,  creatin,  and  creatinin  may  also 
be  present.  The  total  normal  solids  are  composed  approxi- 
mately of  50%  urea,  25%  chlorid  of  sodium;  at  least  one  half 
of  the  remainder  are  phosphates  and  sulphates.  We  see  that 
the  constituent  which  most  influences  the  specific  gravity  is  the 
urea,  and  in  normal  samples  the  specific  gravity  is  an  index  of 
the  amount  of  urea  present.  The  total  solids  may  be  calculated 
by  multiplying  the  last  two  figures  of  the  specific  gravity  by 
2^*  which  will  give  approximately  the  number  of  grams  of  solids 
in  one  liter  of  urine;  from  this  the  solids  in  the  twenty-four- 
hour  amount  may  be  easily  calculated. 

Urea. 

The  chemistry  of  urea  has  been  already  considered  (page 
232). 

Detection.  —  A  qualitative  test  for  this  substance  is  obvi- 
ously superfluous,  although  such  may  be  made  by  obtaining 
the  crystals  of  urea  nitrate  or  oxalate  (page  233).  The  quan- 
tity of  urea  is  of  great  importance,  especially  in  cases  where 
there  is  any  question  in  regard  to  the  body  metaboHsm  or  the 
amount  of  nitrogen  excreted.  By  far  the  greater  proportion 
of  all  nitrogenous  waste  is  ehminated  by  the  kidneys  in  the 
form  of  urea,  a  comparatively  shght  amount  as  other  nitroge- 

*  Coefficient  of  Haeser. 
348 


NORMAL  CONSTITUENTS  OF   URINE 


349 


nous  constituents  of  the  urine,  a  still  smaller  amount  in  the  feces, 
and  traces  only  by  other  avenues.  The  urea  may  be  quanti- 
tatively determined  by  various  methods,  the  hypobromite 
method  being  the  most  practical. 

Quantitative  Determination.  —  There  are  various  forms  of 
apparatus  used  in  connection  with  this  process. 

The  one  devised  by  Dr.  Squibb  is  pictured  in  Fig.  28.  It 
has  been  quite  generally  used;  hence  its  description  is  given. 
It  is  not  recommended,  because  a  source  of  considerable  error 


Fig.  28. 


lies  in  the  fact  that  the  gases  (CO2  and  N)  evolved  from  the  urea 
are  very  apt  to  be  driven  over  into  bottle  A  before  all  the  CO2 
has  been  absorbed  by  the  reagent  in  B  and  consequently  the 
results  are  higher  than  they  should  be. 

The  first  step  in  the  use  of  this  apparatus  is  to  completely 
fill  the  bottle  A,  including  the  tubes  D  and  H,  with  water, 
with  the  glass  plug  E  closing  the  lower  end  of  D.  Next  put 
5  c.c.  each  of  a  40%  solution  of  caustic  soda  and  a  bromine 
solution  in  potassium  bromide*  into  B.  Place  the  stopper  in 
B  and  connect  the  tube  C  at  H,  then  fill  accurately  the  2-c.c. 
pipette  with  urine.  Place  in  position  in  the  stopper  of  B 
as  shown  in  the  cut,  remove  E  from  the  rubber  tube  D,  and 

*  For  preparation  of  this  solution  see  Appendix. 


3SO 


URINE 


allow  D  to  fall  to  the  bottom  of  the  graduate  as  indicated. 
Pressure  is  now  applied  to  the  bulb  of  the  pipette,  so  that  the 
2  c.c.  of  urine  is  forced  with  moderate  rapidity  into  the  bottle. 
As  the  pressure  on  the  bulb  is  released,  water  will  be  drawn 
back  into  A,  and  it  is  essential  that  the  end  oi  D  he  under  water 
during  this  part  of  the  process.  Bottle  B  should  be  agitated 
to  insure  complete  decomposition  of  the  urea.  Nitrogen  and 
carbon  dioxid  are  at  once  evolved  according  to  the  reaction  on 
page  233.  The  40%  solution  of  caustic  soda  is  strong  enough  to 
absorb  and  hold  the  C02-  The  nitrogen  passes 
into  A,  forcing  a  corresponding  volume  of  water 
into  the  graduate.  This  volume  of  gas,  read  in 
cubic  centimeters  of  the  water,  will  give  the 
percentage  of  urea  in  the  sample  examined,  i  c.c. 
of  nitrogen  being  equivalent  to  0.126  gram  of 
urea. 

The  Doremus-Hinds  apparatus  shown  in 
Fig.  29  gives  a  perfectly  satisfactory  method 
for  the  estimation  of  urea  by  the  hypobromite 
method.  The  reagent,  equal  parts  of  bromin 
solution  and  40%  NaOH  (Appendix,  page  380), 
is  introduced  into  R  and  the  tube  completely 
filled.  The  tube  U  is  next  filled  exactly  to  the  o  mark,  then  by 
means  of  the  stop-cock  5  i  c.c.  of  urine  is  allowed  to  enter  T 
a  few  drops  at  a  time  and  slowly  enough  to  prevent  any  escape 
of  gas  through  R.  The  gas  rises  in  small  bubbles  through  a 
comparatively  long  tube  and  remains  in  contact  with  the  reagent 
which  insures  perfect  absorption  of  CO2,  thus  overcoming  the 
greatest  objection  to  the  Squibb's  apparatus. 

The  tube  T  is  graduated  to  read  centigrams  of  urea  in  i  c.c. 
of  urine. 

Uric  Acid. 
Uric  acid  and  its  antecedents,  the  xanthin  bases,  are  derived 
from   the   decomposition   of   nuclein   and   nucleoprotein.     For 


Fig.  29. 


NORMAL   CONSTITUENTS  OF   URINE  35 1 

chemistry  of  this  substance,  see  pages  235  to  237.  The  uric 
acid  is  increased  by  a  highly  nitrogenous  diet  and  certain  vege- 
table substances  which  contain  purin  (page  235)  derivatives, 
such  as  coffee,  tea,  and  cocoa.  The  so-called  red  meats,  beef, 
mutton,  etc.,  are  regarded  as  the  most  abundant  source  of  uric 
acid  and  urates.  As  previously  suggested  uric  acid  does  not 
occur  in  normal  urine  as  such,  but  is  combined  with  the  alka- 
hne  bases. 

Detection.  —  It  is  unnecessary  to  make  a  qualitative  test  in 
urine,  as  urates  are  always  present.  If  a  quaHtative  test  is  de- 
sired the  murexid  test,  as  given  on  page  239,  is  available.  Uric 
acid  is  most  conveniently  determined  quantitatively  by  the 
centrifugal  method  as  devised  by  Dr.  R.  Harvey  Cook.*  The 
detail  of  this  method  is  as  follows:  Measure  10  c.c.  of  urine  into 
a  graduated  tube,  used  in  the  centrifugal  machine,  add  a  few 
grains  of  sodium  carbonate,  and  about  3  c.c.  of  strong  ammo- 
nium hydrate.  Place  in  the  centrifuge,  and  allow  to  run  for  one- 
or  two  minutes,  then  carefully  decant  the  clear  urine  into  another- 
graduate  tube,  leaving  the  precipitate  which  consists  of  earthy 
phosphates.  The  bulk  of  this  precipitate  may  be  noticed  and 
an  idea  obtained  as  to  whether  the  earthy  phosphates  are  present 
in  normal  quantities  or  not.  To  the  clear  urine  add  2  or  3  c.c. 
of  ammoniacal  silver-nitrate  solution  (AgNOs,  5  grams;  dis- 
tilled water,  80  c.c;  strong  ammonia,  20  c.c),  and  run  in  the 
centrifuge  till  the  precipitate  of  silver  urate  has  reached  its 
lowest  obtainable  reading.  The  ammonia  will  prevent  the  pre- 
cipitation of  chlorids  and,  unless  iodids  or  bromids  are  present,, 
the  precipitate  will  be  fairly  pure  silver  urate,  each  tenth  of  a. 
cubic  centimeter  of  the  precipitate  being  equivalent  to  0.001176 
gram  of  uric  acid  in  the  10  c.c.  of  urine  used,  or  0.01176%. 

The  silver  precipitate  is  by  no  means  pure  silver  urate, 
many  of  the  other  nitrogenous  bases  in  urine  forming  insoluble 
silver  salts.     These  occur  only  in  very  slight  traces;    so,  for 

*  Medical  Record,  Mar.  12,  1898,  p.  373. 


352  URINE 

clinical  purposes,  the  method  is  available  unless  the  sample 
contains  bromids  or  iodids,  when  iodid  or  bromid  of  silver  will 
be  formed,  insoluble  in  the  amount  of  ammonia  usually  used. 
More  accurate  results  may  be  obtained  by  either  Hopkins'  or 
FoHn's  method.  These  are  somewhat  similar  and  consist  of  pre- 
cipitation of  the  uric  acid  as  ammonium  urate.  loo  to  200  c.c. 
of  urine  is  used  and  the  precipitation  effected  by  a  saturated 
solution  of  NH4CI  (Hopkins'  method)  or  10  grams  ammonium 
sulphate  (Fohn's  method). 

The  precipitate  is  washed  in  the  reagent  and  dissolved  in 
boihng  water  and  the  amount  of  uric  acid  determined  by  titra- 
tion with  N/20  permanganate  of  potassium.  Each  cubic  centi- 
meter of  KMn04  used  is  equal  to  0.00375  grams  of  uric  acid. 

Ammonia  Determination. 

The  amount  of  ammonia  normally  present  in  urine  is  about 
0.7  gram  in  the  24-hour  amount.  Ammonia  is  increased  in  any 
systemic  condition  resulting  in  an  increase  of  acidic  elements 
(Acidosis),  or  upon  ingestion  of  ammonium  salts  of  inorganic 
acids,  i.e.,  salts  not  easily  oxidized  to  urea. 

Normally,  the  quantity  of  NH3  follows  more  or  less  closely 
the  urea  and  the  protein  metabolism,  and  amounts  to  about 
one-half  of  one  per  cent  or  about  0.7  gram  in  24  hours. 

Determination  may  be  made  as  follows: 

FoHn's  New  Method.  —  Measure  by  use  of  standardized 
"Ostwald  pipette"  i  or  2  c.c.  of  urine  into  a  large  Jena  test- 
tube.  Then  proceed  exactly  according  to  method  given  for 
saliva  on  page  320. 

Formaldehyd  Method.  —  Place  10  c.c.  urine  in  a  250  c.c. 
Erlenmeyer  flask,  add  50  or  60  c.c.  H2O,  titrate  with  N/io  NaOH 
with  phenolphthalein  as  an  indicator.  The  amount  of  NaOH 
used  will  represent  total  acidity  of  sample. 

After  exact  neutralization  add  10  c.c.  of  previously  ne;utra- 
lized  commercial  formaldehyd  solution  and  titrate  again  with 


NORMAL   CONSTITUENTS  OF   URINE  353 

N/io  NaOH.     The  second  amount  of  alkali  added  represents 

ammonia  as  follows: 

4  NH4CI  +  6  CH2O  +  4  NaOH  =  N4(CH2)6  +  10  H2O  +  4  NaCl. 

As  the  ammonium  salts  and  the  caustic  soda  react  molecule 
for  molecule  it  is  possible  to  make  calculation  for  quantity  of 
NH3  by  multipl3dng  the  N/io  factor  (0.0017)  by  the  number  of 
cubic  centimeters  of  N/io  NaOH  used. 

In  cases  of  diabetes  when  the  ammonia  reaches  a  compara- 
tively large  amount  the  figures  obtained  by  this  process  will  be 
found  to  be  a  little  high,  as  amino-acids  are  also  acted  upon  by 
the  NaOH,  and  will  be  calculated  as  ammonia,  but  for  ordinary 
work  or  clinical  comparisons  this  method  is  very  simple  and 
sufficiently  accurate. 

This  method  is  not  affected  by  urea,  uric  acid,  creatin, 
creatinin,  purin  bases  or  hippuric  acid.* 

Chlorids. 

The  chlorids  are  represented  in  the  urine  chiefly  by  sodium 
chlorid.  This  is  present  to  the  extent  of  from  12  to  20  grams  in 
twenty-four  hours.  An  increase  above  this  quantity  is  unusual, 
although  it  simply  indicates  an  increase  in  the  ingested  salt, 
and  is  without  cHnical  significance.  The  chlorin  is  diminished 
in  dropsy,  acute  stages  of  pneumonia,  and  in  fevers  generally. 

Detection.  —  The  usual  qualitative  test  with  silver  nitrate  and 
nitric  acid  is  employed  for  detection  of  chlorid  in  the  urine. 
If  one  drop  of  a  strong  solution  of  silver  nitrate  (i  to  8)  is 
allowed  to  fall  into  the  wine-glass  in  which  the  albumin  test 
has  been  made  (q.  v.),  the  appearance  of  the  resulting  precipi- 
tate will  give  a  rough  idea  of  the  quantity  of  chlorin  present. 
If  a  solid  ball  of  silver  chlorid  is  formed  which  does  not  become 

*  Dr.  Hans  Malfatti  in  Zeit.  fixr  Anal.  Chemie,  47,  page  273. 
Note.  —  See  also  the  Vacuum  Distillation  Method,  giving  very  exact  results 
when  properly  carried  out: 

H.  Bjorn  Andersen  und  Marius  Lauritzen,  Zeit.  fiir  Physiol.  Chemie,  64, 
page  21. 


354  URINE 

diffused  upon  gently  agitating  the  contents  of  the  glass,  the 
chlorin  is  normal  or  increased.  If  the  precipitate  falls  as  a 
cloud  distributed  throughout  the  liquid,  the  chlorin  is  dimin- 
ished. The  chlorin  may  be  determined  by  precipitation  with 
silver  nitrate  in  lo  c.c.  of  urine,  and  the  precipitate  settled  in  a 
centrifuge-tube  to  constant  reading,  but  this  method  is  not 
recommended,  as  the  precipitate  is  a  bulky  one,  and  usually 
takes  a  long  time  for  thorough  settling.  The  titration  with 
silver  nitrate,  using  potassium  chromate  as  an  indicator,  really 
takes  less  time,  and  is  much  more  accurate.  This  titration  is 
made  in  the  usual  way  (see  page  149),  except  that,  inasmuch  as 
phosphates  and  urates  are  also  precipitated,  from  three-tenths  to 
I  c.c.  may  be  deducted  from  the  amount  of  the  silver-nitrate 
solution  used  according  as  it  is  much  or  little,  thus  allowing 
for  these  substances.  An  accurate  titration  of  chlorin  may  be 
made  by  acidifying  the  urine  with  nitric  acid,  adding  an  excess 
of  standard  silver-nitrate  solution,  and  titrating  back  with  a 
standardized  sulphocyanate  solution  (preferably  of  the  same 
strength  as  the  AgNOs  solution),  using  ferric  sulphate  as  an 
indicator.  But,  as  a  rule,  the  simpler  method  gives  results 
which  for  clinical  purposes  are  equally  valuable  with  those  of 
this  more  tedious  though  more  accurate  process. 

Phosphates. 

The  phosphates  in  the  urine  are  of  two  kinds,  the  alkaline 
phosphates,  Na2HP04  and  NaH2P04,  etc.,  and  the  earthy  phos- 
phates represented  by  the  magnesium  and  the  calcium  phosphates. 
The  phosphates  are  normally  present  to  the  extent  of  two  and  a 
half  to  three  and  a  half  grams,  calculated  as  P2O5  (in  twenty-four 
hours) . 

The  triple  phosphates,  ammonium  magnesium  phosphates 
(Plate  IV,  Fig.  2,  p.  163),  are  the  forms  in  which  phosphoric  acid 
is  usually  found  in  urinary  sediment.  Crystals  of  acid  calcium 
phosphate  are  occasionally  found,  and  resemble  the  acid  sodium 


NORMAL  CONSTITUENTS  OF   URINE  355 

urate  in  form  (Plate  X,  Fig.  3,  p.  368),  except  that  they  are 
usually  a  Uttle  broader  and  more  often  occur  in  fan-shaped 
clusters.  They  may  be  distinguished  by  treatment  with  acetic 
acid,  which  dissolves  the  calcium  phosphate  promptly,  while  the 
urate  is  slowly  dissolved  and  crystals  of  uric  acid  appear  after 
a  Httle  time.  The  phosphates  are  deposited  from  neutral  or 
alkahne  urines  and  when  this  precipitation  takes  place  within 
the  body,  the  crystals  cause  more  or  less  irritation  to  the  urinary 
tract  and  may  form  aggregations  which  result  in  calculi.  Phos- 
phates are  supplied  by  either  a  cereal  or  meat  diet.  They  may 
be  much  increased  in  diseases  accompanied  by  nervous  waste, 
or  by  softening  and  absorption  of  bone.  Phosphates  are  dimin- 
ished in  gout,  in  chronic  diseases  of  the  kidney,  and  during 
pregnancy. 

Detection.  —  A  qualitative  test  for  earthy  phosphates 
(E.P.)  may  be  made  by  taking  a  test-tube  half-full  of  urine,  and 
making  alkahne  with  ammonium  hydrate.  When  the  precipi- 
tate has  thoroughly  settled,  if  it  is  about  1/4  to  1/2  inch  in 
depth,  it  represents  normal,  earthy  phosphates.  If  this  mixture 
is  now  filtered,  the  alkaline  phosphates  (A.P.)  may  be  deter- 
mined in  the  filtrate  by  the  addition  to  the  solution  of  one-third 
its  volume  of  magnesium  mixture.*  The  precipitate  after 
settling  will  be  1/2  to  3/4  of  an  inch  in  depth  if  normal.  The 
total  phosphates  may  be  determined  in  the  centrifugal  machine 
by  adding  5  c.c.  of  magnesium  mixture  to  10  c.c.  of  urine.  Each 
tenth  of  a  cubic  centimeter  of  the  centrifugalized  sediment  will  be 
equivalent  to  0.0225  of  P2O5. 

A  more  accurate  determination  of  the  total  phosphoric  acid 
may  be  made  by  the  titration  with  uranium  nitrate  or  acetate 
solution  as  follows: 

Reagent  Required.  —  First.  A  standard  solution  of  uranium 
nitrate  or  acetate  made  by  dissolving  35.5  grains  of  pure  salt 
(the  molecular  weights  of  the  two  salts  differ  so  little  that  the 

*  See  Appendix. 


356  URINE 

same  weight  of  either  may  be  used)  in  sufficient  water  to  make 
I  GOO  c.c. 

Second.  A  sodium  acetate  solution  containing  loo  c.c. 
of  30%  acetic  acid  and  100  grams  of  sodium  acetate  in  enough 
distilled  water  to  make  1000  c.c. 

Third.  An  indicator  consisting  of  a  saturated  solution  of 
potassium  ferrocyanid. 

Process.  —  Place  50  c.c.  of  urine  with  5  c.c.  of  sodium 
acetate  solution  above  described  in  a  small  Erlenmeyer  flask 
and  heat  nearly  to  the  boiling-point.  Titrate,  while  hot  (80° 
or  above),  with  the  standard  uranium  solution  till  a  drop  of  the 
mixture  placed  on  a  white  porcelain  tile  with  a  drop  of  the  indi- 
cator (K4FeCy6)  gives  a  distinct  brown  color.  This  method  of 
determining  the  end  point  is  known  as  "  spotting"  and  with  a 
little  practice  gives  very  accurate  results. 

The  number  of  cubic  centimeters  of  uranium  solution  multi- 
plied by  o.oi  will  give  the  weight  of  P2O5  in  100  c.c.  of  urine 
(i  c.c.  of  reagent  being  equal  to  0.005  gram  P2O5). 

Sulphates. 

The  sulphates  in  the  urine  are  present  as  alkaline  sulphates, 
K2SO4  and  Na2S04;  also  as  ethereal  sulphates,  represented  by 
such  compounds  as  indoxyl  potassium  sulphate,  page  250. 

Detection  and  Determination.  —  The  sulphates  may  be  de- 
tected by  precipitation  with  barium  chlorid  in  HCl  solution.  If 
the  precipitate  is  obtained  from  10  c.c.  of  urine  and  centrifugal- 
ized  to  constant  reading,  the  per  cent  of  sulphuric  acid  by  weight 
will  be  one  fourth  of  the  volume  per  cent  of  the  precipitate. 
The  sulphates  follow  rather  closely  the  urea,  and  their  determi- 
nation is  not  of  great  importance.  They  are  increased  in  acute 
fevers,  diminished  in  chroiiic  diseases  generally,  and  markedly 
diminished  in  carbolic-acid  poisoning.     (Ogden.) 

Coloring  Matter.  —  Urobihn,  an  important  coloring  matter 
of  the  urine,  exists  as  a  parent  substance  or  chromogen  to  which 


NORMAL  CONSTITUENTS  OF  URINE  357 

has  been  given  the  name  urobilinogen.  This  undergoes  decom- 
position by  action  of  Kght  with  Hberation  of  urobihn. 

Urobihn  is  without  doubt  derived  from  the  bilerubin  of  the 
bile,  which,  in  turn,  comes  from  the  hemochromogen  of  the  blood. 
Dr.  J.  B.  Ogden  is  authority  for  the  statement  that  "it  is  safe 
to  infer  that  the  amount  of  urobihn  in  the  urine  is  a  measure  of 
the  destruction  of  the  hemoglobin  or  blood  pigment. " 

Urochrome  is  a  pigment  to  which  the  yellow  color  of  urine 
is  chiefly  due.  Uroerythrin  and  urorosein  are  less  important, 
existing  only  in  very  slight  quantities,  but  they  are  responsible 
for  colors  of  some  sediments  and  of  decomposition  products 
which  are  noticed  in  analysis. 

Indoxyl. 

The  indoxyl  is  of  considerable  importance,  as  an  increase 
above  the  normal  amount  is  indicative  of  increased  putrefaction 
of  nitrogenous  substances  taking  place  in  the  small  intestine. 
Indoxyl  may  also  be  increased  by  acute  inflammatory  process 
of  the  peritoneal  cavity.  Ordinary  constipation  does  not  in- 
crease the  indoxyl.  The  test  for  indoxyl  depends  upon  the 
oxidation  of  the  indoxyl  potassium  sulphate  to  indigo  blue 
according  to  the  following  reaction : 

2  C8H6NKSO4  +  O2  =  2  CgH5N0  +  2  KHSO4. 

Indoxyl  potassium  sulphate.  Indigo. 

Detection  and  Determination.  —  15  c.c.  of  strong  HCl  is 
placed  in  a  wine-glass,  and  a  single  drop  of  concentrated  nitric 
acid  added;  then  30  drops  of  urine  are  stirred  into  the  mixture. 
If  indoxyl  is  present,  an  amethyst  color  develops  in  from  five  to 
fifteen  minutes.  If  the  color  is  purple,  the  indoxyl  is  increased. 
Variation  of  the  amount  of  indoxyl  within  normal  limits  is 
rather  wide,  and  the  indoxyl  may  be  reported  as  high  or  low 
normal,  increased,  or  diminished. 


CHAPTER  XXXIX. 
ABNORMAL  CONSTITUENTS  OF  URINE. 

The  principal  abnormal  constituents  are  albumin,  sugar, 
acetone,  bile,  and  various  crystalline  salts,  discoverable  either 
by  microscopical  examination  of  the  sediment,  or  by  evapora- 
tion of  a  clear  fluid,  and  examination  with  the  micropolari- 
scope. 

Metallic  substances,  arsenic,  lead,  and  mercury  are  occa- 
sionally present,  and  tests  should  be  made  for  them  when  gen- 
eral symptoms  or  the  conditions  of  the  kidney  indicate  metallic 
poison.  Albumin  is  probably  present  in  minute  traces  in  the 
majority  of  urines.  When  in  sufficient  quantity  to  be  detected 
by  the  usual  laboratory  methods,  it  is  essential  that  we  learn 
the  source  from  which  it  has  been  derived,  for  the  simple  pres- 
ence of  even  a  considerable  trace  of  albumin  may  be  of  but 
slight  cHnical  importance.  Albumin  may  indicate  either  a 
pathological  condition  of  the  kidney,  which  allows  the  entrance 
into  the  renal  tubules  of  serum-albumin  from  the  blood,  or  it  may 
indicate  a  change  in  the  composition  of  the  blood,  whereby  the 
albumin  passes  more  easily  through  the  renal  membranes,  or  its 
presence  may  be  due  to  irritations  from  various  sources  of  the 
urinary  tract;  and,  as  regards  the  bearing  of  albuminurias  on 
dental  disease,  it  is  sufficient  simply  to  determine  whether  renal 
disturbance  is  primary  or  secondary  to  some  other  trouble,  such 
as  heart  disease;  or  purely  local,  as  when  caused  by  irritation  due 
to  crystalline  elements. 

Detection.  —  Albumin  may  be  detected  by  either  of  two 
simple  methods.  It  is  often  desirable  to  use  both  of  these 
methods,    thereby    eliminating    possible    confusion    from    the 

3S8 


ABNORMAL   CONSTITUENTS  OF   URINE  359 

presence  of  substances  other  than  albumin,  which  may  respond 
to  one  of  the  two  tests,  but  not  to  both. 

The  first  consists  simply  in  underlaying  about  25  c.c.  of 
filtered  urine  in  a  wine-glass  with  concentrated  nitric  acid. 
The  wine-glass  should  be  tipped  as  far  as  possible  and  the  acid 
allowed  to  run  very  slowly  down  the  side.  This  method  is  pref- 
erable to  the  use  of  the  apparatus  known  as  the  albuminoscope 
or  Horismascope   (Fig.  30).     As  this  latter  mxthod  does  not 


Fig.  30.  Fig.  31. 

provide  for  sufficient  mixing  of  nitric  acid  with  the  sample,  the 
albumin  is  shown  by  a  narrow  white  ring  at  the  plane  of  contact 
of  the  two  liquids.  A  white  ring  above  the  plane  of  contact  is 
not  albumin,  but  is  composed  of  acid  urates,  indicating  an  excess 
of  urates  in  the  sample  (Fig.  31).  The  albumin,  in  distinction 
from  this  band,  occurs  directly  above  the  acid  and  is  usually 
reported  as  the  slightest  possible  trace  when  just  discernible; 
as  a  slight  trace,  when  well  marked,  but  not  dense  enough  to 
be  seen  by  looking  through  the  liquid  from  above;  as  a  trace, 
when  the  white  cloud  may  be  seen  by  looking  down  into  the 
glass  from  above  and  a  large  trace  if  plainly  visible  in  this  way. 
Acetic  acid  and  heat  method  of  testing  for  albumin  is  the 
other  method  referred  to  in  the  preceding  paragraph.  It  is  of 
about  the  same  delicacy  as  the  nitric  acid  test,  and  is  less  liable 
to  respond  to  substances  other  than  albumin.  It  is  made  as 
follows : 


360  URINE 

A  test-tube  is  filled  two  thirds  full  of  perfectly  clear  filtered 
urine,  one  drop  of  acetic  acid  added  and  the  upper  half  of  the 
sample  boiled.  The  tube  can  easily  be  held  in  the  hand  by  the 
lower  end.  After  boiling,  if  the  tube  is  examined  before  a  black 
background,  a  slight  cloudiness  or  turbidity  resulting  from 
coagulated  albumin  can  be  easily  detected  in  the  upper  part  of 
tube.  Anything  more  than  a  trace  should  be '  determined  in 
the  centrifugal  machine  by  mixing  10  c.c.  of  filtered  urine 
with  about  2  c.c.  of  acetic  acid  and  3  c.c.  of  potassium 
ferrocyanid  solution.  Each  tenth  of  a  cubic  centimeter 
of  the  precipitated  albumin,  when  settled  to  constant 
reading,  indicates  one  sixtieth  of  one  per  cent  albumin 
by  weight.  This  factor  is  fairly  correct  up  to  four  or 
five  tenths  of  a  cubic  centimeter  of  precipitate;  beyond 
this  it  is  of  little  value,  and  the  albumin  is  best  deter- 
mined quantitatively  by  measuring  50  or  100  c.c.  of 
urine  into  a  small  beaker,  adding  a  drop  of  acetic  acid, 
and  boiling,  which  will  completely  precipitate  the  al- 
bumin. It  may  then  be  filtered  into  a  counterpoised 
filter,  thoroughly  washed,  first  in  water,  next  in  alcohol, 
and  lastly  in  ether,  dried  at  a  temperature  a  little 
'  below  the  boiling-point  of  water,  and  weighed.  Esbach's 
method  may  be  of  value  in  some  instances,  and  is  carried  out 
as  follows: 

Fill  the  albuminometer  (Fig.  32)  with  urine  to  the  line  U, 
and  then  add  the  reagent*  to  the  line  R\  close  the  tube,  mix  the 
contents  thoroughly,  and  allow  to  stand  in  an  upright  position 
for  twenty-four  hours.  At  the  end  of  that  time  the  depth  of 
precipitate  may  be  read  by  the  figures  on  the  lower  part  of  the 
tube,  these  figures  representing  tenths  of  one  per  cent  of  albu- 
min, or  grams  of  albumin  in  a  liter  of  urine.  If  a  sample  of 
urine  contains  more  albumin  than  is  easily  estimated  by  the 

*  Esbach's  reagent  consists  of  picric  acid,  10  grams;  citric  acid,  20  grams,  and 
distilled  water  sufficient  to  make  one  liter. 


ABNORMAL  CONSTITUENTS  OF   URINE  361 

centrifugal  or  Esbach's  method,  approximate  results  will  be 
obtained  by  diluting  with  several  volumes  of  distilled  water, 
until  the  quantity  of  albumin  precipitated  is  within  the  limit 
of  the  test.  The  proteoses  occasionally  occur  in  the  urine,  and 
are  distinguished  from  albumin  by  the  fact  that  they  redissolve 
at  a  boiling  temperature.  If  filtered  while  hot,  albumin,  which 
usually  accompanies  them,  will  remain  on  the  paper,  while 
albumose  will  separate  out  from  the  clear  filtrate  as  it  cools. 

Sugar. 

Sugar  in  urine  represents  a  perverted  process  of  oxidation 
for  which  the  liver  is  largely  responsible.  The  pancreas  also 
often  plays  an  important  part  in  cases  of  diabetes,  but  just 
how  this  is  done  is  not  clearly  known.  Sugar  in  the  urine 
does  not  of  necessity  indicate  diabetes  any  more  than  albumin 
indicates  Bright's  disease.  Many  cases  of  glycosuria  are  of  a 
temporary  nature  and  respond  readily  to  dietary  treatment. 
Whenever  sugar  is  found  it  is  desirable  to  make  tests  upon  both  a 
fasting  and  an  after-meal  sample,  such  as  might  be  obtained 
^  before  breakfast  and  one  hour  after  dinner.  If  the  fasting  sample 
is  comparatively  free  from  sugar,  it  indicates  that  the  glycosuria 
is  of  a  temporary  nature  and  due  to  faulty  metabolism,  rather 
than  to  any  organic  disease  of  the  liver  or  pancreas. 

Detection.  —  Sugar  in  the  urine  may  be  detected  by  several 
general  carbohydrate  tests,  as  previously  given.  The  one  which 
is  most  valuable  and  most  generally  employed  is  Fehling's 
test  (Exp.  136,  page  262).  It  is  best  to  modify  this  test  by 
bringing  the  FehHng's  solution  to  active  ebullition,  adding  from 
5  to  30  drops  of  the  suspected  sample  and  allowing  to  stand 
without  further  heating.  This  prevents  possible  reduction  of 
the  sugar  by  xanthin  bases  or  other  occasional  constituents  of 
the  urine,  which  might  give  misleading  results  if  the  mixture 
'  were  boiled  after  addition  of  the  sample.  There  is  less  danger 
of  trouble  of  this  sort  if  the  gravity  of  the  urine  is  below  normal. 


362  URINE 

If  it  is  necessary  to  make  a  rapid  test,  the  mixture  may  be  boiled 
after  the  urine  is  added,  and  in  case  the  result  is  negative  there 
is  no  need  of  further  test;  if,  however,  a  slight  reduction  of  the 
copper  solution  takes  place,  it  will  be  necessary  to  repeat  the 
test,  using  the  precaution  above  given.  The  fermentation  test 
(Exp,  140,  page  262)  may  also  be  used  to  detect  the  presence  of 
sugar  and,  approximately,  the  amount.  The  phenyl-hydrazine 
test  may  be  used  as  a  confirmatory  test  or  in  cases  where  very 
minute  quantities  are  suspected.  This  test  is  considered  about 
ten  times  as  delicate  as  the  Fehhng's  test;  consequently,  it  may 
show  small  amounts  of  sugar  which  are  not  detected  by  the 
more  rapid  process.  Quantitatively,  sugar  may  be  determined 
by  the  use  of  Fehhng's  solution  as  follows: 

If  the  urine  contains  more  than  a  trace  of  albumin,  this 
substance  should  be  removed  by  adding  a  drop  of  acetic  acid 
and  heating;  after  filtration  the  sample  should  be  cooled  and 
restored  to  original  volume  with  distilled  water.  If  specific 
gravity  of  the  urine  is  more  than  1025,  it  should  be  diluted  to 
ten  times  its  volume  with  distilled  water  (urine,  one  part;  water, 
nine).  If  the  gravity  is  less  than  1025  dilute  it  to  five  times  its 
volume,  mix,  and  fill  a  25  c.c.  burette.  In  a  250  c.c.  flask  place 
ID  c.c.  each  of  the  alkahne  tartrate  and  copper  sulphate  solu- 
tions (Fehhng's  solution),  and  add  about  100  c.c.  of  distilled 
water.  Place  the  flask  over  a  Bunsen  burner,  and  bring  to  a 
boil.  If  no  change  takes  place  after  a  minute  or  two  of  boihng, 
add  the  solution  from  the  burette  gradually,  until  the  precipitate 
becomes  sufficiently  dense  to  obscure  the  blue  color  of  the  solu- 
tion. Continue  to  boil  for  one  or  two  minutes,  then  remove 
from  the  flame  and  watch  carefully  the  line  directly  beneath 
the  surface  of  the  Kquid,  which  will  appear  blue  until  all  of 
the  copper  has  been  reduced  to  the  red  suboxid.  The  solution 
should  be  kept  at  the  boiling-point  throughout  the  entire  oper- 
ation, except  in  making  the  examination  of  the  meniscus  between 
the  additions  of  the  diluted  urine.     These  additions  must  be 


ABNORMAL   CONSTITUENTS  OF   URINE  363 

made  very  carefully,  and  as  the  process  nears  completion  not 
more  than  one  or  two  drops  should  be  added  at  a  time.  When 
the  blue  color  has  entirely  disappeared,  and  the  line  of  meniscus 
has  become  colorless,  note  the  number  of  cubic  centimeters  of 
dilute  urine  used,  and  calculate  that  in  that  quantity  there  is  an 
equivalent  of  0.05  gram  of  glucose;  in  other  words,  0.05  gram 
of  glucose  will  exactly  reduce  the  amount  of  Fehling's  solution, 
used,  and  from  this  fact  the  amount  of  glucose  in  the  entire 
twenty-four  hour  amount  of  urine  is  easily  calculated.  If  the 
titration  is  carried  beyond  the  proper  "end  point"  the  meniscus, 
will  appear  yellow  instead  of  colorless. 

The  fermentation  test  for  sugar  is  a  convenient  and  easily 
made  qualitative  test,  it  being  only  necessary  to  fill  a  fermen- 
tation tube  (Fig.  17,  page  263)  absolutely  full  of  urine  to  which 
a  small  portion  of  yeast  has  been  added,  and  to  allow  the  tube 
to  stand  in  a  warm  place  for  several  hours.  Any  collection  of 
gas  in  the  top  of  the  tube  will  indicate  the  presence  of  sugar.. 
This  method  may  also  be  used  as  a  quantitative  test  for  sugar 
by  taking  two  portions  of  the  same  sample,  adding  yeast  to- 
one,  and  using  the  other  as  a  control.  At  the  end  of  twenty- 
four  hours,  CO2  is  removed  from  fermented  sample,  the  specific 
gravity  of  both  samples  is  carefully  taken,  and  the  loss  of 
density  in  the  fermented  sample  is  calculated  as  sugar  by  multi- 
plying the  number  of  degrees  lost  in  gravity  by  0.23,  water 
being  considered  as  1000. 

The  optical  analysis  for  sugar  may  be  made  with  a  polariscope,, 
preferably  constructed  for  use  on  urine.  This  determination 
depends  upon  the  ability  of  glucose  to  rotate  the  plane  of  polar- 
ized light  toward  the  right,  the  degree  of  rotation  indicating 
the  amount  of  sugar  in  a  pure  solution.  Of  course,  allowance 
or  correction  must  always  be  made  for  the  presence  of  any  sub- 
stances which  will  rotate  the  hght  in  the  opposite  direction, 
such  as  albumin,  laevulose  and  /3  oxybutyric  acid. 

For  the  detail  of  construction  and  use  of  the  polariscope, 


364  URINE 

the  student  is  referred  to  the  more  complete  works  on  urine 
analysis  by  Ogden,  Holland,  or  Purdy. 

Acetone. 

Acetone  may  occur  in  the  urine  as  a  result  of  various  patho- 
logical conditions  and  according  to  von  Noorden  they  are  all 
due  to  some  one-sided  perversion  of  nutrition.  The  aceto- 
nurias  attendant  on  diabetes,  scarlet  fever,  pneumonia,  small- 
pox, etc.,  are  of  less  practical  interest  to  the  dental  practitioner 
than  those  more  often  overlooked  by  the  medical  profession, 
and  which  indicate  improper  diet,  possibly  resulting  in  serious 
malnutrition.  The  following  points  may  be  noted:  In  ad- 
vanced stages  of  diabetes,  acetone  appears  in  the  urine  accom- 
panied by  diacetic  acid.  An  increased  ingestion  of  proteins 
may  result  in  the  appearance  of  acetone,  in  which  case  the  direct 
cause  is  more  an  "insufficient  utiUzation  of  carbohydrates"* 
than  the  increase  of  protein.  Acetone  may  result  from  the  oxi- 
dation of  /3  oxybutyric  acid.  Diacetic  acid  is  first  formed,  and 
subsequently  the  carboxyl  group  is  replaced  by  'an  atom  of 
hydrogen,  as  shown  by  the  following  graphic  formulas: 

,8  oxybutyric  acid:   CH3-CHOH-CH2-COOH. 
Diacetic  acid:   CH3-CO-CH2-COOH. 
Acetone:   CH3-CO-CH3. 

Detection.  —  Acetone  may  be  detected  in  the  urine  by  the 
production  of  iodoform,  as  described  under  analysis  of  saliva 
on  page  321,  but  it  is  not  in  this  case  nearly  so  delicate  a  test 
on  account  of  the  odor  and  acid  character  of  the  urine.  A 
more  useful  test  is  known  as  Legal's  test  and  is  made  as  follows: 
To  a  third  of  a  test-tubeful  of  urine  add  a  few  drops  of  a  freshly 
prepared  and  fairly  concentrated  solution  of  sodium  nitro- 
prussid,  next  add  two  or  three  drops  of  strong  acetic  acid,  and 
then  a  considerable  excess  of  ammonia.     If  the  contents  of  the 

*  Von  Noorden's  Diseases  of  Metabolism  and  Nutrition. 


ABNORMAL   CONSTITUENTS  OF   URINE  365 

tube  are  mixed  by  a  rather  rapid  rotary  motion  without  invert- 
ing or  violent  shaking,  the  ammonia  will  not  reach  the  bottom 
of  the  tube,  and  the  presence  of  acetone  will  be  indicated  by  a 
violet-red  band  above  the  layer  of  acid  liquid.  If  much  acetone 
is  present  a  deep  violet  to  purple  color  is  obtained. 

Diacetic  Acid  occasionally  occurs  in  urine  as  an  abnormal 
constituent  most  commonly  in  advanced  stages  of  diabetes, 
usually  accompanied  by  acetone  and  /3  oxybutyric  acid.  It 
may  be  detected  by  adding  to  the  urine  a  Httle  ferric  chlorid, 
when  a  dark  wine  red  color  is  produced.  If  a  precipitate  of 
ferric  phosphate  is  obtained,  filter  the  urine  and  examine  the 
filtrate  for  color.  This  test  may  be  made  fairly  distinctive  for 
diacetic  acid  by  boiling  and  cooling  a  second  portion  of  the 
urine  previous  to  making  the  test,  when  the  result  will  be  nega- 
tive if  the  color  at  first  produced  was  due  to  diacetic  acid. 

Bile. 

Bile  may  occur  in  the  urine  as  such,  due  to  pathologic  con- 
ditions of  the  liver-  or  bile-ducts,  as  stated  on  page  338.  The 
coloring  matters  of  the  bile  may  also  occur  from  causes  aside 
from  lesions  of  the  liver.  A  urine  containing  bile  or  bile-pig- 
ments is  always  more  or  less  highly  colored,  and  upon  shaking 
the  foam  will  be  of  a  yellow  or  greenish-yellow  color.  Albumin 
and  high  indoxyl  accompany  the  presence  of  bile  and  there  is 
also  usually  considerable  renal  disturbance.  It  may  be  detected 
by  carefully  adding  to  one-half  a  wine-glass  of  the  suspected 
sample  a  few  cubic  centimeters  of  the  alcoholic  solution  of  iodin 
(tincture  of  iodin) .  A  green  color  will  be  observed  just  beneath 
the  Hne  of  contact  of  the  two  liquids  (page  341).  The  test  may 
be  conveniently  made  by  placing  the  iodin  first  in  the  wine-glass 
and  then  with  a  pipette  introducing  the  urine  beneath  the  iodin 
solution. 


366  URINE 

Metallic  Substances. 

Arsenic,  mercury,  and  lead  are  the  three  metals  which  it 
may  be  necessary  to  look  for  in  a  sample  of  urine.  The  method 
for  the  detection  of  mercury,  given  on  page  330,  is  appHcable 
for  this  purpose. 

Arsenic  may  be  detected  by  the  Marsh-Berzelius  test  (page 
29),  after  oxidizing  all  organic  matter.  The  process  may  be 
carried  out  as  follows:  Evaporate  to  dryness  a  liter  of  urine, 
to  which  200  c.c.  of  strong  nitric  acid  has  been  added;  add  to 
the  residue,  while  still  hot,  from  15  to  20  c.c.  of  concentrated  sul- 
phuric acid.  This  must  be  done  in  a  large  porcelain  evaporat- 
ing-dish,  or  else  the  acid  must  be  added  very  slowly  to  prevent 
frothing  over  and  loss  of  a  portion  of  the  sample.  After  the 
action  has  quieted  down  the  whole  mixture  may  be  trans- 
ferred to  a  500  c.c.  Kjeldahl  flask  and  heat  applied  gradually  at 
first,  and  then  more  strongly.  It  will  be  necessary  to  add  from 
time  to  time  small  portions  of  nitric  acid  and  possibly  a  little 
more  sulphuric  acid;  as  the  oxidation  progresses  the  liquid  in  the 
flask  becomes  lighter  in  color  and  at  the  completion  of  the  process 
is  water-white,  even  when  the  temperature  is  increased  so  that 
sulphuric-acid  fumes  are  given  off.  After  cooling,  the  strongly 
acid  Hquid  is  diluted  with  four  or  five  times  its  volume  of  water, 
filtered,  if  necessary,  to  remove  excessive  amounts  of  earthy  sul- 
phates, and  is  then  ready  for  the  arsenic  test. 

Lead.  —  The  sample  of  urine  to  be  tested  for  lead  should 
measure  at  least  1000  c.c,  and  should  be  tested  for  iodin  to 
insure  the  fact  that  the  patient  has  been  under  treatment  with 
potassium  iodid  to  dissolve  lead  salts,  otherwise  a  negative 
result  may  be  obtained  when  lead  is  actually  present  and  poison- 
ing the  system.  Oxidize  the  sample  in  precisely  the  same  manner 
as  when  making  the  arsenic  test,  up  to  the  point  of  diluting  the 
strong  acid  solution  with  water;  then,  in  this  case,  use  rather  less 
water  for  the  dilution,  allow  to  cool,  and  neutraHze  with  Squibb's 


ABNORMAL   CONSTITUENTS  OF   URINE  367 

ammonia,  acidify  quite  strongly  with  acetic  acid,  and  pass  H2S 
gas  into  the  solution.  It  is  desirable  to  leave  the  solution  satu- 
rated with  H2S  for  at  least  twelve  hours.  Then  filter,  and  with- 
out washing  dissolve  the  precipitate  in  warm  dilute  nitric  acid, 
evaporate  the  HNO3  solution  to  dryness,  add  5  c.c.  of  water, 
make  alkaline  with  a  drop  or  two  of  ammonia,  and  again  acidify 
with  acetic  acid  and  add  a  solution  of  bichromate  of  potash.* 
Allow  to  stand  several  hours,  filter  off  the  chromate  of  lead,  wash 
several  times  with  distilled  water,  and  lastly  with  H2S  water 
when  the  lead  chromate  will  blacken  from  the  formation  of  lead 
sulphid.  This  stain  is  a  superficial  one  and  disappears  upon 
standing,  but  when  the  process  is  conducted  in  this  way  it  con- 
stitutes a  very  delicate  and  satisfactory  test  for  lead  in  either 
urine  or  saliva. 

Urinary  Sediments. 
The  sediment  which  settles  from  a  sample  of  urine  upon 
standing  consists  normally  of  a  shght  amount  of  mucin  and 
epithelial  cells.  It  may  contain  also  bacteria  and  a  consider- 
able variety  of  extraneous  matter,  including  starch  grains, 
various  vegetable  spores,  yeast  cells,  fibers  from  various  fabrics, 
cotton,  wool,  flax  from  linen,  etc.,  diatoms,  scales  from  insects' 
wings,  and  other  particles  which  may  occur  as  dust  (see  Plate 
IX,  Fig.  6;  also  Plate  X,  Fig.  4).  Under  abnormal  conditions 
the  sediment  may  contain  crystalHne  elements,  including  uric 
acid  and  urates,  phosphates,  oxalates,  cystin,  tyrosin,  leucin,  etc., 
also  organized  elements  such  as  epithehum,  renal  or  other  casts 
(Plate  IX,  Fig.  4),  blood  globules,  pus  cells  (Plate  IX,  Fig.  3), 
spermatozoa  (Plate  IX,  Fig.  2),  fat,  mucin  (Plate  IX,  Fig.  5),  etc. 
Urinary  sediment  may  be  thrown  down  from  a  fresh  specimen 
by  the  use  of  the  centrifugal  machine,  or  it  may  be  allowed  to 
stand  in  a  glass  tube  with  rounded  bottom  for  several  hours,  when 
the   sediment  settles   to   the  bottom  by  gravity.     If  possible 

*  Natural   chromate  of  potash  will   precipitate   copper,    the   acid   chromate 
precipitates  lead  only  of  the  second  group  metals. 


368  URINE 

it  is  best  to  examine  sediments  settled  in  both  of  these  ways, 
as  the  centrifuge  will  show  elements,  such  as  small  casts,  that 
would  settle  slowly,  possibly  not  at  all,  by  the  gravity  method. 
On  the  other  hand,  the  sediment  allowed  to  settle  spontane- 
ously will  often  give  a  more  correct  idea  of  comparative  num- 
bers of  the  various  elements  observed,  than  when  settled  in  a 
centrifuge-tube.  A  drop  or  two  of  formalin  may  be  used  to 
preserve  urinary  sediment,  as  suggested  on  page  344,  but  if  too 
much  of  this  substance  is  used,  especially  in  urines  containing 
high  percentages  of  urea,  a  compound  is  liable  to  be  formed  which 
has  been  called  formaldehydurea  (Plate  X,  Fig.  5),  which  settles 
with  the  sediment  and  seriously  interferes  with  the  micro- 
scopical examination.  This  compound  may  form  sheaf-like 
crystals  similar  to  tyrosin  and  may  be  mistaken  for  crystals  of 
sodium  oxalate,  especially  when  examined  with  a  low  power 
objective. 

Uric  Acid.  —  Uric  acid  is  deposited  from  normal  urine,  upon 
standing,  with  an  excess  of  free  acid  (HCl).  Urines  that  have 
a  high  degree  of  acidity  will  also  produce  a  like  deposit,  and  the 
finding  of  uric-acid  crystals  does  not  necessarily  signify  that 
the  crystalKzation  took  place  within  the  body,  unless  special 
care  has  been  taken  that  the  sample  examined  was  perfectly 
fresh,  although  the  tendency  to  deposit  uric  acid  is,  of  course, 
indicated.  The  urine  from  which  uric  acid  separates,  as  such, 
is  usually  rather  concentrated  and  of  strong  acid  reaction. 
These  crystals  vary  in  appearance  (Plate  X,  Figs,  i  and  2), 
but  are  almost  always  colored  yellow  to  red.  Colorless  crystals 
are  sometimes  observed.  They  are  usually  quite  small,  but  of 
the  pecuhar  whetstone  shape  in  which  this  acid  most  usually 
crystallizes.  The  presence  of  uric  acid  has  practically  no  effect 
upon  the  acidity  of  the  sample;  for,  if  the  acid  separates  in  a 
crystalline  form,  it  is  insoluble,  and  if  it  does  not  separate  it  is 
in  combination  as  urates,  possibly,  of  course,  as  acid  urates. 
Uric  acid  exists  normally  in  proportion  to  urea  as  about  i  to  50, 


PLATE   IX.  — URINE. 


Fig.  I. 
Ammonium  Acid  Urate. 


Fig.  3.  —  Pus. 
A ,  After  addition  of  Acetic  Acid. 


Fig.  2. 
Spermatozoa. 


Fig.  4. 
Renal  Casts. 


Fig.  5. 
False  Casts  and  Mucin. 


Fig.  6. 
A,  Lycopodium;  B,  Moth-scales;  C,  Cork; 
D,  Cotton-iibres;  E,  Wool-fibres. 


ABNORMAL   CONSTITUENTS  OF    URINE  369 

but  there  is  no  necessary  relationship  between  the  quantities 
of  the  two  substances,  and  the  one  may  be  diminished  while 
the  other  is  increased. 

Urates.  —  Urates  may  occur  as  crystalline  or  amorphous  pre- 
cipitates. The  crystalline  urates  are  urate  of  sodium  rarely,  acid 
urate  of  sodium  (Plate  X,  Fig.  3,  p.  368),  and  acid  ammonium 
urate  (Plate  IX,  Fig.  i,  p.  367).  The  amorphous  urates  are  of  the 
alkaline  bases,  usually  sodium,  and  are  frequently  precipitated 
by  lowering  of  the  temperature  after  the  sample  has  been  passed, 
in  such  cases  the  urine  assumes  a  cloudy  appearance  which  is 
cleared  up  by  the  application  of  heat.  A  sediment  consisting 
of  urates  is  usually  of  a  pinkish  color. 

Phosphates.  —  Phosphates  in  the  urinary  sediment  may  be 
amorphous  or  crystalline.  They  are  of  the  alkaline  earths 
rather  than  of  the  alkaline  metals,  as  the  latter  are  soluble  in 
both  the  acid  and  neutral  forms.  The  amorphous  phosphates 
deposit  with  the  change  of  reaction  from  acid  to  alkahne,  and 
usually  in  the  form  of  a  so-called  triple  phosphate  of  ammonia 
and  magnesia  (Plate  IV,  Fig.  2,  p.  163).  This  salt  crystallizes  in 
two  forms.  The  prismatic  form  is  the  ultimate  form;  that  is,  if 
the  crystallization  takes  place  very  slowly,  the  prismatic  form  is 
the  one  in  which  the  salt  is  thrown  out.  If  it  takes  place  rapidly 
it  may  be  precipitated  in  the  feathery  form,  but  this  slowly 
changes  over  to  the  prismatic  form.  The  acid  phosphates  may 
be  precipitated  closely  resembHng  in  appearance  the  acid  urates 
(Plate  X,  Fig.  3),  but  may  be  distinguished  from  them  by  their 
ready  solubility  in  acetic  acid  and  failure  to  produce,  after  solu- 
tion in  acetic  acid,  any  crystals  of  uric  acid  such  as  are  obtained 
from  the  urates. 

Acid  Lactates.  —  These  are  soluble  salts,  and  are  found  in 
urine  only  by  evaporation  of  a  drop  of  the  clear  fluid  and  an 
examination  of  the  residue  by  polarized  light.  When  found  in 
the  urine,  the  significance  is  quite  different  from  that  when  found 
in  the  saliva,  as  in  the  urine  they  may  possibly  be  formed  from 


370  URINE 

lactates,  which  indicate  a  faulty  action  of  the  liver,  and  of  course 
they  have  no  connection  with  tooth  erosion.  The  lactates  fur- 
nish evidence  of  similar  character. 

Oxalates.  —  Oxalates  if  found  in  the  sediment  usually  occur 
as  calcium  oxalates.  These  crystals  assume  a  variety  of  forms, 
as  shown  in  Plate  II,  Fig.  i,  p.  162.  Sodium  oxalate  (Plate  II, 
Fig.  4)  may  occur  in  the  urine  (not,  however,  in  the  sediment) , 
and  is  detected  only  by  evaporating  a  drop  of  the  clear  liquid 
and  examining  with  polarized  light.  Dr.  Kirk  claims  that  an 
oxaluria  may  be  in  this  way  detected  for  a  considerable  time 
before  the  appearance  of  the  oxalate  of  lime  crystals,  and  hence 
such  examination  becomes  a  valuable  aid  to  diagnosis. 

Cystin.  —  Cystin  occurs  as  six-sided  plates.  It  is  a  com- 
paratively rare  crystal,  and  indicates  insufficient  oxidation,  par- 
ticularly of  the  organic  sulphur  compounds. 

Epithelium.  —  Epithelium  occurs  in  the  urinary  sediment 
from  any  part  of  the  urinary  tract.  In  the  male  urine  it  is 
much  easier  to  determine  the  character  of  the  epithelium  than 
in  the  female,  as  in  the  latter  the  comparatively  large  amount 
of  mucous  surface,  from  which  epithelium  may  be  gathered, 
furnishes  a  great  variety  of  forms  which  are,  of  course,  without 
cHnical  significance.  The  epithelium  from  the  vagina  may  be 
quite  readily  distinguished  as  very  large  cells  with  small  nuclei, 
lying  usually  in  masses  overlapping  one  another  but  with  com- 
paratively slight  density.  Renal  epithelium  may  be  found  as 
small,  round  cells,  differing  but  slightly  in  size  from  a  leucocyte. 
They  may  be  a  httle  larger,  a  little  smaller,  or  about  the  same 
size.  They  are  round  and  more  or  less  granular  in  appearance. 
Epithelium  from  the  bladder  varies  considerably,  but  the 
majority  of  cells  would  properly  come  under  the  general  head 
of  squamous  epithelium,  rather  large  and  flat  with  a  distinct 
nucleus  of  medium  size.  Epithelial  cells  from  the  neck  of  the 
bladder  in  male  urine  are  quite  typical,  being  round  and  com- 
paratively dense  with   a  prominent  nucleus.     They  are   four 


PLATE  X— URINE. 


Fig.  I. 
Uric  Acid. 


Fig.  3. 
A,  Sodium  Urate;  B,  Sodium  Acid  Urate. 


Fig.  2. 
Uric  Acid. 


Peg.  4. 

Yeast  Cells  and  Molds. 


Fig.  5. 
Formaldehyd  Urea  (P.  L.). 


Fig.  6. 
Cystin. 


ABNORMAL   CONSTITUENTS  OF   URINE  37 1 

or  five  times  the  size  of  a  leucocyte  and,  in  cases  of  irritation 
at  the  neck  of  the  bladder,  are  usually  present  in  considerable 
numbers  and  of  quite  uniform  appearance. 

Renal  casts  consist  of  molds  formed  within  the  tubules  of 
the  kidneys  which  retain  the  form  of  the  tubules  after  expul- 
sion into  the  bladder.  According  to  Ogden  the  most  probable 
theory  of  their  formation  is  "  that  they  are  composed  of  coagu- 
lable  elements  of  blood  that  have  transuded  into  the  renal  tubules, 
through  pathologic  lesions  of  the  latter,  and  have  there  sohdified 
to  be  later  voided  with  the  urine,  as  molds  of  the  tubules." 
Casts  are  termed  blood  casts,  pus  casts,  epithehal  or  fat  casts 
according  as  these  elements  may  adhere  with  more  or  less  pro- 
fusion to  the  cast  itself.  Pure  hyahne  casts  are  pale,  perfectly 
transparent  cyHnders,  with  at  least  one  rounded  end  which 
can  be  plainly  seen,  and  may  occur  occasionally  in  urine  from 
perfectly  healthy  individuals.  Fibrinous  casts  are  highly  refrac- 
tive and  when  seen  by  white  light  are  of  a  yellowish  color  and 
indicate  acute  renal  disturbance.  Waxy  casts  resemble  the 
so-called  fibrinous  as  regards  density,  but  they  have  no  color, 
and  usually  indicate  advanced  and  serious  stages  of  kidney 
disease,  while  the  presence  of  fibrinous  casts  has  no  necessarily 
serious  significance. 

Blood  and  Pus  are  readily  recognized  under  the  micro- 
scope after  a  very  little  practice.  The  blood  disks  are  circular 
and  show  a  characteristic  biconcavity  in  the  alternate  shading 
of  the  edge  and  center  by  slight  changes  of  focus.  The  red 
corpuscles  usually  show  a  shade  of  color  by  white  light.  The 
pus  corpuscles  or  leucocytes  are  larger  than  the  red  corpuscles, 
and  are  granular  in  appearance.  Treatment  with  acetic  acid 
destroys  the  granular  matter  and  brings  into  prominence  the 
cell  nuclei,  two  or  three  in  number.  If  the  leucocytes  are  free 
and  scattered  they  should  not  be  regarded  as  pus  but  be  reported 
simply  as  an  excess  of  leucocytes ;  if  they  are  very  numerous  and 
occur  in  clumps  they  constitute  pus. 


372  URINE 

Spermatozoa.  —  Occasional  spermatozoa  may  be  found  in. 
sediment  from  either  male  or  female  urine  and  are  without  clin- 
ical significance.  If  persistent  and  in  considerable  numbers, 
seminal  weakness  is  indicated  (Plate  IX,  Fig.  2,  p.  367). 

Fat  occurs  in  urinary  sediment  as  small  globules,  highly 
refractive  and  varying  greatly  in  size.  They  are  frequently 
adherent  to  cells  or  to  casts.  Fatty  casts  indicate  a  fatty  de- 
generation, which  may  or  may  not  result  from  chronic  disease. 
Fat  may  be  demonstrated  by  staining  with  osmic  acid  which 
is  reduced  by  the  double-bonded  fatty  constituent  (olein), 
leaving  a  black  deposit  which  stains  the  globule. 

Mucin  appears  in  the  sediment  as  long  and  more  or  less 
indistinct  threads.  An  excessive  amount  usually  indicates  irrita- 
tion of  some  mucous  surface.  The  source  would  have  to  be 
determined  by  other  more  characteristic  elements  (Plate  IX, 

Fig.  S)- 

The  salts  which  may  be  obtained  by  evaporation  of  a  drop 
of  clear  urine  and  detected  by  the  micropolariscope  are  simi- 
lar to  those  occurring  in  the  saliva;  sodium  oxalate  is  prob- 
ably most  frequently  found.  If  the  gravity  is  above  normal 
the  urea  often  crystalHzes,  making  it  somewhat  difficult  to 
pick  out  the  abnormal  crystalline  constituents.  Phosphates 
are  also  usually  observed,  but  these  crystals  are  large  and  as  a 
rule  prismatic,  not  easily  mistaken  for  anything  else. 

Interpretation  of  Results. 

As  stated  at  the  beginning  of  the  chapter  on  urine,  our  object 
has  been  the  study  of  this  secretion  from  the  standpoint  of  gen- 
eral metabolism,  rather  than  with  a  view  to  differentiate  various 
forms  of  renal  disease,  and  while  it  is  important  that  the  presence 
of  renal  disease  should  be  recognized,  its  further  investigation 
constitutes  a  proper  study  for  the  physician  rather  than  for 
the  dentist,  and  when  such  conditions  are  found  to  exist  a 
patient's  physician  should  be  apprised  of  the  fact. 


ABNORMAL  CONSTITUENTS  OF   URINE 


373 


The  discussion  of  a  few  examples  based  upon  actual  analyses, 
may  serve  to  show  deductions  which  may  be  drawn  from  analyses 
of  saliva  and  urine. 


No. 


URINE. 


Name. 


Date, 


Per  cent. 


0.88 
0.034 


Anal,  for  Dr.  C.  A.  J. 

24  h.  Am't.  2000  c.c. 
Sp.Gr.1013.  Reaction  Ac. +  (50' 

Color  =N.  Sulph. 

Ind.      =+  E.  Phos.- 

Bile.  A.  Phos.- 

Diac.  Ac.  Acetone  =  abs. 

Alb.  =  SI.  possible  trace. 

Soluble  Salts  (cryst.)     Occasional  sodium  oxalate. 
Sediment.     Occasional  leucocytes,  few  neck  of  bladder  cells,  an  excess  of 
mucin. 


Urea 

Uric  Ac. 

Ammon. 

Chlor.  0.455 

Phos.  Ac.    0.09 

Sugar  =  abs. 

Uric  Ac.  to  Urea  =  I  to  24, 


Grams  in 
24  hours. 
17.6 
0.68 


9.1 

1.8 


ANALYSIS  OF  SALIVA. 
Dr.  C.  A.  J.  February,  1906. 

Appearance  =  cloudy.  Odor  =  slight. 

Reaction  =  strongly  acid.  Specific  gravity  =  1003. 

Mucin  =  slight.  Albumin  =  marked. 

Ammonia  =  increased,  but  inferior  to      Glycogen  =  negative. 

sulphocyanate  which  is  very  high. 
Chlorin  =  normal  or  slightly  increased. 
Soluble  salts  =  lactates,  alkaline  chlorids. 
Abnormal  constituents  =  lactic  acid. 
Sediment  =  heavy,  excess  of  leucocytes, 

mucin,  and  squamous  epithelium. 
Indicated  diathesis  =  hyperacid. 

As  we  study  these  analyses,  we  notice  first  in  the  urine  an 
increased  quantity  with  low  urea.  These  things  accompany 
chronic  kidney  disease,  but  inasmuch  as  in  this  case  we  find  no 
casts  in  the  sediment,  and  no  more  albumin  than  can  be  ac- 
counted for  by  the  slight  irritation  at  the  neck  of  the  bladder, 
we  consider  the  dilution  unimportant.  The  uric  acid  is  high 
in  proportion  to  the  urea,  and  the  chlorin  being  nearly  normal 
for   the   twenty-four-hour   amount  would  indicate  a  full  diet 

*  The  abbreviations  used  in  this  analysis  are  as  follows:  N  =  normal,  Ac.  == 
acid,  SI.  =  slight.  The  minus  sign  =  diminished  or  decreased,  the  plus  sign  =  ex- 
cessive or  increased,  Abs.  =  absent. 


374 


URINE 


with  perverted  oxidation.  These  indications  are  of  probabil- 
ities rather  than  positive  conclusions,  although  in  this  partic- 
ular case  the  actual  facts  were  as  indicated.  The  high  indoxyl 
in  the  absence  of  any  acute  disease  would  indicate  an  increased 
putrefaction  in  the  small  intestine,  probably  due  to  defective 
intestinal  digestion. 

The  condition  of  the  saHva,  together  with  the  urine  analysis, 
would  indicate  a  condition  favorable  to  erosion  of  the  teeth 
and  the  development  of  pyorrhoea.  It  was  found  that  the 
patient  was  not  suffering  from  erosion  of  the  teeth,  except  in 
a  very  shght  degree,  but  the  evidences  of  pyorrhoea  were  quite 
marked  at  the  time  of  the  first  examination  some  weeks  before 
the  analyses  were  made. 


No.  2. 


URINE. 


Name. 


Date, 


Per  cent. 

Grams  in 
24  hours. 

Urea             2.27 

25.24 

Reaction  =  Ac. 

Uric  Ac.      0.051 

0.61 

Sulph. 

Ammon. 

E.  Phos.  =  N. 

Chlor.          0.834 

lO.I 

A.  Phos.  =  N. 

Phos.  Ac.    0.112 

1-3 

Acetone  =  Abs. 

Sugar  Abs. 

Uric  Ac.  to  Urea  =  I 

to 

Anal,  for 

24  h.  Am't.  1200  c.c. 
Sp.  Gr.  =  1023 
Color  =  SI.  high. 
Ind.  N. 
Bile. 

Diac.=Ac. 

Alb.  SI.  possible  trace. 
Soluble  Salts  (cryst.) 
Sediment.  —  Numerous   large  calcium   oxalate   crystals,   occasional  uric- 
acid  crystals,  excess  of  mucin,  rarely  a  blood  globule. 

The  saliva  accompanying  this  sample  indicated  a  hyper- 
acid diathesis  and  a  sHght  amount  of  pus  in  the  sediment, 
otherwise  nothing  abnormal.  In  this  sample  we  notice  a  con- 
centrated urine  with  a  tendency  to  precipitation  of  crystalline 
elements  which  have  apparently  produced  a  slight  irritation  of 
the  urinary  passages,  as  indicated  by  the  blood  globules,  and  the 
sHghtest  possible  trace  of  albumin.  The  patient  in  this  case 
was  a  young  man  in  good  general  health,  a  student  at  the  Dental 
School.  An  incipient  pyorrhoea  had  been  noticed,  and,  as  a 
result  of  information  gained  by  this  analysis,  the  red  meat, 
coffee,  and  other  uric-acid-producing  foods  were  wholly  ehmi- 


ABNORMAL  CONSTITUENTS  OF   URINE 


375 


ated  from  the  diet,  and  improvement  of  the  conditions  of  teeth 
and  gums  followed.  It  is  not  necessary  to  assume  that  the 
next  case  of  this  character  would  respond  to  similar  treatment. 


URINE. 


Name.     P.  J. 


No.  3. 

Date,  Dec.  '05. 


Phys.     Dr.  R. 


24  h.  Am't.  =  2200  c.c.  Sp.  Gr.  =  1026      N.% 

Color  =N.        Reaction  =  Ac.  +  Urea         =2.65     (2.0) 


Uph.  =S1.- 
Ind.  =S1.- 
Bile     =Abs. 


E.  Phos.   =N. 
A.  Phos.   =N. 


Uric  Ac.   =0.047   (0-033) 

Chlor.       =0.625   (0.67) 

Phos.  Ac.  =  0.16     (0.18) 


Grams  in 
24  hours. 

58.3 
1.03 

13-7 
35 


N. 
(28.0) 
(0.5) 
(10. o) 
(  2.7) 


Acetone  very  slight  trace.     Sugar  =  slight  trace  present 
Alb.  =  SI.  possible  trace. 

Sediment.  —  Calcium  oxalate  crystals  very  numerous,   occasional  leuco- 
cyte, occasional  blood  globule  with  rarely  a  hyaline  cast. 

(The  numbers  in  parentheses  are  the  average  normal.) 

This  urine  was  from  a  patient  with  a  tendency  to  diabetes  who 
was  living  almost  exclusively  on  a  protein  diet.  This  accounted 
for  the  high  uric  acid  and  high  urea.  There  was  a  sHght  irritation 
of  the  kidneys  which  was  secondary  to  the  glycosuria.  There  was 
no  trouble  with  the  teeth  and  no  examination  of  saHva  was  made. 

The  following  sample  indicates  a  chronic  disease  of  the  kidneys, 
and  it  was  thought  wise  to  have  the  day  and  night  twelve-hour 
quantities  measured  separately  as,  in  cases  of  chronic  kidney 
disease,  the  night  quantity  usually  exceeds  the  day  quantity, 
and  this  fact  is  often  a  valuable  aid  in  determining  the  character 
of  kidney  disturbances.  The  metaboHsm  in  this  case  is  good, 
the  nephritis  being  only  at  an  early  stage. 


No. 


URINE. 


Name. 


Date, 


Anal,  for 

24  h.  Am't.  2500  c.c. 
Sp.  Gr.  1012.  Reaction  N. 

Color  pale.  Sulph. 

Ind.-  E.  Phos.- 

Bile.  A.  Phos. 

Diac.  Ac.  Acetone  Abs. 

Alb.  SI.  trace. 
Soluble  Salts  (cryst.). 
Sediment.  —  Squamous  epithelium  with  several  hyaline  and  fine  granular 
casts. 


Per  cent. 

Grams  in 
24  hours. 

Urea 

1 .01 

25-25 

Uric  Ac. 

0.020 

0-50 

Ammon. 

Chlor. 

0.315 

7.87 

Phos.  Ac 

.      O.QO 

2.25 

Sugar  Abs. 

Uric  Ac. 

to  Urea  =  I 

to 

376 


URINE 


The  following  is  a  case  of  chorea  and  is  of  interest,  particu- 
larly, on  account  of  the  large  number  of  sodium  oxalate  crys- 
tals which  were  persistently  present. 


URINE. 


Name.  M.G. 


No.  5. 
Date,  March  28,  1912. 


Anal,  for 

Per  cent. 

Grams  in 
24  hours. 

24  h.  Am't.  473  c.c. 

Urea             2.31 

10.93 

Sp.  Gr.  1021. 

Reaction  Ac. 

Uric  Ac.      0.053 

0.251 

Color,  SI.  high. 

Sulph. 

Ammon. 

Ind.  N. 

E.  Phos. 

Chlor.          0.588 

2 .  781 

Bile. 

A.  Phos. 

Phos.  Ac.    0.135 

0.638 

Diac.  Ac. 

Acetone  Abs. 

Sugar  Abs. 

Alb.  SI.  possible  trace. 

Uric  Ac.  to  Urea  = 

I  to 

Soluble  Salts  (cryst.).     Sodium  oxalate  crystals,  phosphatic  crystals. 
Sediment.  —  Leucocytes,  epithelium. 

As  seen  by  these  examples,  it  is  necessary  to  take  the  whole 
analysis  into  consideration,  often  in  conjunction  with  an  analysis 
of  the  saliva,  in  order  to  know  just  what  the  system  is  doing, 
and  whether  there  is  possible  systemic  derangement  which 
may  have  an  important  bearing  on  conditions  found  in  the  oral 
cavity.  Experience  and  study  alone  will  enable  one  to  correctly 
interpret  the  results  of  such  analyses,  but  it  has  been  our  aim 
to  give  sufficient  groundwork  for  the  prosecution  of  such  study, 
and  to  show  that  in  many  cases  the  knowledge  derived  from 
thorough  examinations  may  be  of  the  greatest  importance  in 
the  successful  treatment  of  diseased  conditions. 


APPENDIX. 


Ammonia  (dilute).  —  Strong  ammonia  one  part,  distilled 
water  two  parts. 

Ammonium  Molybdate  Solution  for  Phosphates.  —  This  may 
be  made  by  dissolving  20  grams  of  ammonium  molybdate  in  a 
mixture  of  250  c.c.  NH4OH  and  250  c.c.  of  water.  Then  this 
solution  is  added  to  1000  c.c.  of  nitric  acid  making  1500  c.c.  of 
reagent.  In  using  this  solution  as  a  test  for  phosphates  it  is. 
necessary  to  heat  the  mixture  to  about  60°  C.  The  test  is  less 
delicate  than  if  made  with  reagent  prepared  as  follows: 

Dissolve  100  grams  of  molybdate  trioxid  (molybdic  acid) 
in  400  c.c.  of  dilute  NH4OH  (10%).  Allow  to  cool  and  add 
all  at  once  1000  c.c.  of  dilute  HNO3  (HNO3  3  parts,  H2O  2  parts). 
The  precipitate  first  formed  is  immediately  redissolved  and  the 
product  should  be  a  perfectly  clear,  nearly  colorless  solution. 
This  reagent  acts  in  the  cold,  is  more  sensitive  than  that  pro- 
duced by  the  first  formula  and  is  recommended  as  the  better  of 
the  two. 

Barf oed's  Reagent.  —  Dissolve  one  part  of  copper  acetate 
in  fifteen  parts  of  water;  to  each  200  c.c,  of  this  solution  add 
5  c.c.  of  acetic  acid  containing  38  per  cent  of  glacial  acetic  acid. 

Congo  Red.  —  Two  per  cent  aqueous  solution. 

CUSO4  Solution.  —  One  per  cent  for  Biuret  test. 

Preparation  of  Cystin,  Tyrosin,  and  Leucin. 

Cystin.  —  i.  Clean  200  grams  of  hair  by  washing  with  dilute 
HCl  and  then  with  ether.  Boil  the  clean  hair  with  600  c.c.  of 
concentrated  HCl  (specific  gravity,  1.19)  for  four  hours  (in  a 

377 


378  APPENDIX 

three-liter  flask  with  condenser)  on  a  sand-bath  in  hood.     Then 
let  cool. 

2.  Add  concentrated  NaOH  solution  (750  c.c.  H2O,  500 
grams  NaOH)  till  the  reaction  is  only  faintly  acid. 

3.  Add  to  the  solution,  which  has  begun  to  boil  on  neu- 
tralization, plenty  of  animal  charcoal,  and  boil  three-quarters 
of  an  hour. 

4.  Filter  hot,  being  careful  to  moisten  filter  and  funnel  with 
hot  water  to  prevent  funnel  from  cracking. 

5.  The  filtrate  should  be  faintly  yellow.  On  coohng,  a 
crystalline  precipitate  forms,  mainly  cystin,  with  some  tyrosin 
and  leucin.  If  this  is  not  the  case,  or  if  the  precipitate  is  slight, 
the  solution  must  be  concentrated.  Save  the  filtrate,  which 
with  the  filtrate  from  6  is  to  be  worked  up  later  for  tyrosin 
and  leucin. 

6.  After  standing  overnight  filter  off  the  precipitate. 

7.  Dissolve  this  precipitate  in  350  c.c.  of  hot  10  per  cent 
NH4OH  (hood)  and  let  cool.  Then  continue  the  cooling  with 
finely  chopped  ice  or  with  snow.  Filter  off  any  tyrosin  that 
may  have  precipitated,  and  combine  it  with  the  filtrate 
of  6. 

8.  Add  glacial  acetic  acid,  being  careful  not  to  acidify.  The 
precipitate  is  a  mixture  of  tyrosin  and  cystin.     Filter. 

9.  Make  filtrate  from  8  quite  acid  with  glacial  acetic  acid. 
The  precipitate  is  almost  pure  cystin.  Let  stand  twenty-four 
hours.     Then  filter,  and  wash  with  H2O  and  alcohol. 

10.  Recrystallize  by  redissolving  in  as  Httle  hot  10  per 
cent  ammonia  as  is  necessary  to  effect  solution,  cooling  and 
precipitating  with  glacial  acetic  acid. 

The  preparations  should  be  pure  and  contain  no  tyrosin, 
for  which  test  may  be  made  with  Millon's  reagent. 

Reactions.  — •  Put  a  trace  of  cystin  into  a  test-tube  with  some 
dilute  NaOH  and  a  Httle  lead  acetate.  Boil.  H2S  is  formed 
because  S  is  split  off. 


APPENDIX  379 

Tyrosin.  —  i .  Concentrate  the  neutralized  filtrate  of  6  of 
cystin  preparation  till,  on  cooling,  tyrosin  crystallizes  out. 

2.  Filter,  and  save  filtrate  for  the  preparation  of  leucin. 

3.  Dissolve  the  tyrosin  crystals  in  very  little  hot  water. 

4.  Add  amyl  alcohol  till  a  heavy  precipitate  forms. 

5.  Filter  precipitate. 

6.  Redissolve  in  very  little  hot  water,  and  let  crystallize 
out  by  cooling. 

Examine  crystals  under  the  microscope. 
Test  with  Millon's  reagent. 

Leucin.  —  i.  Take  the  filtrate  of  2  in  the  preparation  of 
tyrosin,  and  evaporate  to  dryness  on  the  water-bath. 

2.  Extract  with  alcohol. 

3.  On  standing,  the  leucin  crystallizes  out  of  the  alcohoUc 
extract  as  it  evaporates. 

4.  Filter,  and  dry  the  crystals. 
Examine  under  the  microscope. 

Dimethyl-amino-azobenzene.— 0.5  per  cent  alcoholic  solution. 
Esbach's  Reagent.  —  See  page  360. 

Fehling's  Solution.  —  The  Fehling's  solution  recommended 
for  experiments  in  this  book  is  one-half  the  strength  frequently 
employed,  and  is  prepared  in  separate  solutions  as  follows: 
Dissolve  34.639  grams  of  pure  crystallized  copper  sulphate  in 
water,  and  make  solution  up  to  one  liter.  This  constitutes  the 
first  part  of  the  reagent.  The  second  part  may  be  made  by 
dissolving  173  grams  of  Rochelle  salt  and  52.7  grams  of  caustic 
soda  (NaOH)  in  water  and  making  up  to  one  liter.  When  pre- 
pared in  this  way  10  c.c.  of  each  of  these  solutions  mixed  to- 
gether will  be  reduced  by  0.05  gram  of  glucose. 

Ferric  Chlorid.  —  2.5  per  cent.     Solution  acidified  with  HCl. 

Glycogen  (CeHioOs)!!.  —  Use  a  liver  taken  from  an  animal 
just  killed,  or,  if  the  season  permits,  oysters  just  removed  from 
the  shell.  Cut  an  oyster,  as  rapidly  as  possible,  into  small 
pieces,  and  throw  it  into  four  times  its  weight  of  boiling  water, 


380  APPENDIX 

slightly  acidulated  with  acetic  acid.  After  boiling  the  first  por- 
tion for  a  short  time,  remove  the  pieces,  grind  in  a  mortar  with 
some  sand,  return  to  the  water,  and  continue  the  boiling  for  sev- 
eral minutes.  Filter  while  hot.  The  opalescent  solution  thus 
obtained  is  an  aqueous  solution  of  glycogen  and  other  substances. 

If  a  purer  solution  is  desired,  continue  as  follows:  Add 
to  the  filtrate  alternately  a  few  drops  of  HCl  and  potassio- 
mercuric  iodid,  until  a  precipitate  of  protein  ceases  to  form.. 
This  may  be  determined  more  conveniently  by  filtering  off 
a  small  portion  of  the  liquid  from  time  to  time,  and  adding  to 
the  clear  filtrate  the  HCl  and  potassiomercuric  iodid.  When 
the  precipitation  of  the  proteins  is  complete,  filter,  and  to  the 
milky  filtrate  add  double  its  volume  of  alcohol;  the  glycogen 
will  precipitate  as  a  white  powder.  Filter  this  off,  wash  with 
66  per  cent  alcohol  (one  part  of  water  to  two  of  alcohol),  and 
dissolve  in  water. 

Gram's  Solution.  —  Same  as  lodin  Solution  given  below. 

Gunzburg's  Reagent.  —  Phloroglucin,  2  grams;  vanillin,  i 
gram;   alcohol,  100  c.c. 

Hydrochloric  Acid  (dilute) .  —  Hydrochloric  acid,  strong, 
(sp.  gr.  1.20)  one  part;  distilled  water,  two  parts. 

Hypobromite  Solution  for  Urea.  —  Consists  of  a  mixture  of 
equal  parts  of  the  following  solutions: 

Bromin  Solution  for  Urea.  —  125  grams  KBr  and  125  grams 
Br  to  one  Hter  water. 

NaOH  Solution  for  Urea.  —  A  40-per  cent  solution. 

lodin  Solution.  —  10  grams  iodin,  20  grams  KI,  made  up 
with  water  to  one  liter. 

Iodin  Tincture.  —  See  tincture. 

Invertase.  —  Mix  500  gms.  of  ''  beer  yeast,"  200  c.c.  of  water 
and  10  gms.  of  sugar,  allow  to  stand  one  hour.  Add  50  c.c.  of 
60%  alcohol  and  a  little  thymol.  Filter,  press  or  allow  to  dry, 
put  the  nearly  dry  mass  in  a  flask,  add  20  gms.  of  sugar  and 
shake  till  solution  is  effected.     Keep  in  ice  chest. 


APPENDIX  381 

If  "beer  yeast"  is  not  available  a  solution  of  invertase,  rather 
less  satisfactory  than  the  above,  can  be  made  as  follows:  Take 
one  dozen  compressed  yeast  cakes,  grind  with  sand  and  mix 
with  500  c.c.  of  water,  and  a  little  chloroform  as  preservative. 
Allow  to  stand  twelve  hour's  and  filter. 

Leucin.  —  See  under  Cystin,  pages  377,  379. 

Lipase.  —  From  castor  bean.  Remove  the  shells  from  10 
grams  of  fresh  beans,  break  them  up  as  fine  as  possible  and 
allow  to  stand  overnight  in  a  loosely  stoppered  test-tube  full  of 
alcohol  ether  mixture.  Pour  off;  grind  the  beans  to  a  powder 
in  a  small  mortar,  transfer  to  a  test-tube  and  let  stand  under 
ether  overnight.  Filter  with  suction  filter  and  wash  two  or 
three  times  with  small  amounts  of  the  alcohol  ether  mixture. 

Fat  Digestion  with  Lipase  {castor  bean) .  — ■  Grind  with  the 
powder,  in  the  order  named,  5  c.c.  N/io  sulphuric  acid  (sup- 
pHed),  5  c.c.  of  neutral  cotton  oil  (sp.  gr.  0.92)  and  5  c.c.  luke- 
warm water.  The  water  should  be  added  a  little  at  a  time  and 
thoroughly  worked  into  the  mixture  so  that  at  the  end  of  the 
operation  a  good  emulsion  is  secured.  Cover  the  evaporating 
dish  and  let  stand  in  a  warm  place  overnight. 

Add  50  c.c.  of  alcohol,  10  c.c.  ether,  and  a  few  drops  phenol- 
phthalein  and  titrate  with  N/i  sodium  hydrate.  Calculate 
the  amount  of  fatty  acid  and  the  per  cent  of  fat  digestion. 

Lipase.  —  From  pancreas.  Take  a  pig's  pancreas,  remove 
all  fat,  grind  and  allow  to  stand  overnight.  Then  add  four 
times  its  weight  of  25%  alcohol  and  allow  to  stand  three  days. 
Syphon  off  clear  fluid  and  neutralize  with  sodium  carbonate. 
The  solution  will  contain  a  fat-spHtting  enzyme. 

Magnesia  Mixture. — -125  grams  of  ammonium  chlorid, 
125  grams  of  magnesium  sulphate,  dissolved  in  sufficient  water 
to  make  one  liter  of  solution,  then  add  125  c.c.  of  strong  am- 
monia water. 

Mercuric  Chlorid  Solution.  —  Five  per  cent  HgCl2  in  dis- 
tilled water. 


382  APPENDIX 

Millon's  Reagent.  —  To  one  part  of  mercury  add  two  parts 
nitric  acid  of  specific  gravity  1.4,  and  heat  on  the  water-bath 
till  the  mercury  is  dissolved.  Dilute  with  two  volumes  of  water. 
Let  the  precipitate  settle,  and  decant  the  clear  fluid. 

Mucin  Solution.  —  Cut  a  portion  of  a  navel-cord  into  small 
pieces.  Shake  in  a  flask  with  water,  changing  the  water  several 
times.  This  removes  salts  and  albumin.  Extract  for  twenty- 
four  hours  with  Hme-water  or  baryta-water  in  a  corked  flask. 
Filter.  To  filtrate  add  acetic  acid,  which  precipitates  the  mucin. 
Let  settle,  filter,  and  wash  with  water. 

Mucin  may  also  be  prepared  from  the  saliva  by  precipitation 
with  acetic  acid. 

Nessler's  Solution.  —  This  is  an  alkaline  solution  of  mercuric 
iodid,  made  as  follows:  Dissolve  35  grams  of  potassium  iodid  in 
about  200  c.c.  of  water.  Dissolve  17  grams  of  mercuric  chlorid  in 
300  c.c.  of  hot  water.  Add  the  potassium  iodid  to  the  mercuric 
chlorid,  until  the  precipitate  at  first  formed  is  nearly  all  redis- 
solved.  If  the  precipitate  should  entirely  dissolve,  add  a  few 
cubic  centimeters  of  a  saturated  solution  of  mercuric  chlorid, 
until  a  slight  permanent  precipitate  is  obtained.  After  the 
mixture  is  cold,  make  up  to  one  Hter  with  a  20-per-cent  solution 
of  caustic  potash.     Allow  to  settle  and  use  the  clear  solution. 

Nitric  Acid  (dilute).  —  Strong  HNO3  (Sp.  gr.,  1.42)  one  part, 
and  water  three  parts. 

Pancreatic  Extract.  —  Obtain  a  fresh  pancreas  and  soak  in 
four  times  its  weight  of  25%  alcohol  for  two  or  three  days. 
Filter  and  make  the  solution  neutral  or  very  sHghtly  alkaHne 
with  sodium  carbonate.  This  solution  will  contain  the  fat- 
splitting  enzyme. 

Phenoldisulphonic  Acid.  —  Phenoldisulphonic  acid,  for  esti- 
mation of  nitrates  in  water  analysis,  may  be  prepared  by  heat- 
ing on  a  water-bath  for  several  hours  a  mixture  of  555  grams  of 
concentrated  sulphuric  acid  and  45  grams  of  pure  carbolic-acid 
crystals. 


APPENDIX  383 

Phenyl-hydrazine  Solution.  —  i  gram  phenyl-hydrazine  hy- 
drochlorid  and  2  grams  sodium  acetate  dissolved  in  10  c.c. 
water. 

Picric-acid  Solution  (Esbach's  Reagent).  —  Picric  acid,  10 
grams;  citric  acid,  20  grams;  dissolved  in  sufi&cient  water  to 
make  one  Hter. 

Potassium  Ferrocyanide  Solution.  —  Ten  per  cent  K4Fe(CN)6 
in  distilled  water. 

Potassium  Cyanid  (KCITO).  —  Melt  in  an  iron  ladle,  of  at 
least  50  c.c.  capacity,  five  grams  of  commercial  potassium  cyanid, 
and  stir  in  gradually  20  grams  of  Htharge.  When  the  entire 
amount  has  been  added,  pour  the  mass  out  upon  an  iron  plate, 
and  allow  to  cool.  Separate  as  far  as  possible  the  reduced  lead 
from  the  potassium  cyanid  that  has  been  formed,  powder  the 
latter,  and  dissolve  in  25  c.c.  of  cold  H2O.  Filter  if  necessary 
and  purify  by  repeated  crystallization. 

Silver-nitrate  Solution.  —  Drop  solution,  i :  8. 

Quantitative  Solution  for  Chlorin  Titration  in  Urine.  —  29.075 
grams  AgNOs,  made  up  to  one  Hter  with  water,  i  c.c.  of  this 
solution  corresponds  to  o.oi  gram  NaCl  or  0.00607  gram  CI. 

Starch  Paste  (thin).  —  Rub  about  one-half  gram  of  starch  to 
a  thin  paste  with  cold  water.  Add  sufficient  boiHng  water  to 
dissolve,  then  dilute  to  100  or  150  c.c. 

Sulphuric  Acid  (dilute).  —  Twenty  per  cent  strong  H2SO4  in 
distilled  water. 

Tincture  lodin  for  Bile  Test.  —  Dilute  until  just  transparent 
in  test-tube. 

Tropaeolin  00.  —  Saturated  alcoholic  solution. 

Tyrosin.  —  See  paragraph  under  Cystin,  pages  377,  379. 

Uffelmann's  Reagent.  —  Mix  10  c.c.  of  a  4-per-cent  solution 
of  carboKc  acid  with  20  c.c.  of  water,  and  add  a  drop  or  two  of 
ferric  chlorid. 

Urea.  Synthesis  of.  —  Add  to  the  filtered  solution  of  KCNO 
(above)  a  cold  saturated  solution  of  ammonium  sulphate,  con- 


384  APPENDIX 

taining  at  least  six  grams  of  (NH)2S04.  Heat  the  mixture 
slowly  on  a  water-bath  at  a  temperature  of  60°  C,  and  main- 
tain at  that  point  for  one  hour.  By  this  process  ammonium 
cyanate  is  formed  and  then  changed  to  urea,  which  may  be 
obtained  in  an  impure  state  by  evaporating  the  solution  to  dry- 
ness on  a  water-bath,  and  extracting  the  residue  with  hot,  strong 
alcohol.     The  urea  will  crystalHze  from  the  alcohol  as  it  cools. 


APPENDIX 


385 


INTERNATIONAL  ATOMIC  WEIGHTS,  1912. 


Symbol. 

Aluminium 

Al 

Antimony. . 

Argon 

Arsenic .... 

Sb 

A 

As 

Barium. .  .  . 

Ba 

Bismuth. .  . 

Bi 

Boron 

B 

Bromin. .  .  . 

Br 

Cadmium . . 

Cd 

Caesium. .  . 

Cs 

*Calcium.  .  . 

Ca 

Carbon .... 

C 

Cerium .... 

Ce 

Chlorin .... 

CI 

Chromium . 

Cr 

Cobalt 

Co 

Columbium 

Cb 

Copper.  .  .  . 
Dysprosium 
*Erbium. . .  . 

Cu 
Dy 
Er 

Europium. . 
Fluorin.  .  .  . 

Eu 
F 

Gadolinium 

Gd 

Gallium.  .  . 

Ga 

Germanium 

Ge 

Glucinum. . 

Gl 

Gold 

Au 

Helium .... 

He 

Hydrogen.. 
Indium.  .  .  . 

H 

In 

lodin 

I 

Iridium .... 

Ir 

*Iron 

Fe 

Krypton. .  . 
Lanthanum 

Kr 
La 

Lead 

Pb 

Lithium.  .  . 

Li 

Lutecium.  . 

Lu 

Magnesium 

Manganese 

*Mercury. .  . 

Mg 
Mn 
Hg 

Atomic 
Weight. 


27. 1 
120.  2 
39.88 
74.96 

137-37 

208.0 
II  .0 
79.92 

I I 2 . 40 

132.81 
40.07 
12.00 

140.25 
35-46 
52.0 

58.97 

93-5 

63.57 
162.5 
167.7 
152.0 

19.0 

157-3 
69.9 

72.5 

9-1 

197.2 

3-99 
1 .008 
114-8 
126.92 
193 -I 
55-84 
82.92 
139.0 
207. 10 
6.94 
174.0 
24.32 

54-93 
200.6 


Molybdenum 

Neodymium 

Neon 

Nickel 

*Nitron  (radium  emanation) 

Nitrogen 

Osmium 

Oxygen 

Palladium 

Phosphorus 

Platinum 

Potassium 

Praseodymium 

Radium 

Rhodium 

Rubidium 

Ruthenium 

Samarium 

Scandium 

Selenium 

Silicon 

Silver    

Sodium 

Strontium 

Sulphur 

*Tantalum 

Tellurium 

Terbium 

Thallium 

Thorium 

Thulium 

Tin 

Titanium 

Tungsten 

Uranium 

*Vanadium 

Xenon 

Ytterbium  (Neoytterbium) 

Yttrium 

Zinc 

Zirconium 


Symbol 


Mo 

Nd 

Ne 

Ni 

Nt 

N 

Os 

O 

Pd 

P 

Pt 

K 

Pr 

Ra 

Rh 

Rb 

Ru 

Sa 

Sc 

Se 

Si 

Ag 

Na 

Sr 

S 

Ta 

Te 

Tb 

Tl 

Th 

Tm 

Sn 

Ti 

W 

U 

V 

Xe 

Yb 

Yt 

Zn 

Zr 


Atomic 
Weight. 


96.0 

144-3 
20.2 
58.68 

222.4 
14.01 

190.9 
16.00 

106.7 
31.04 

195.2 
39- 10 

140.6 

226.4 

102.9 

85-45 
loi .  7 

150.4 
44-1 
79.2 
28.3 

107.88 
23.00 
87-63 
32.07 

181. 5 

127.5 
159-2 
204.0 
232.4 
168.5 
119. o 

48.1 
184.0 
238.5 

51-0 
130.2 
172.0 

89.0 

65.37 
90.6 


*  Values  that  have  been  changed. 


INDEX 


A. 

Absolute  temperature,  8 

Acetaldehyd,  198 

Acetamid,  226 

Acetanilid,  isocyanid  test  for,  229 

Acetate,  94 

Acetic  acid,  212,  213 

Acetic  acid,  (N/io)  factor,  144 

Acetic  acid,  test  for  (acetates),  94 

Acetic  ether,  207 

Acetic  anhydrid,  214 

Acetone,  202 

bodies,  221 

chloroform,  167 

in  blood,  202 

in  saliva,  determination  of,  321 

in  saliva,  312 

in  urine,  364 
Acetylene,  190 

preparation  of  (Exp.  53),  193 
Acetyl  chloride,  214 

urea,  234 
Achroodextrin,  264 
Acid  albumin,  278 

albuminate,  278,  291 

ammonium  urate,  369 

defined,  3 

groups,  87 

lactates  in  urine,  369 

metaprotein,  291 

metaprotein,    preparation    of    (Exp. 
192),  293 

phosphates,  in  urine,  369 

potassium  oxalate,  218 

protein,  276 

salts,  3 

urates  (ammonium  and  sodium),  369 
Acids  of  group  I,  tests  for,  87 

of  group  II,  tests  for,  89 

of  group  III,  tests  for,  92 

of  group  IV,  tests  for  94 
Acidity  of  saliva,  304 

of  urine,  determination  of,  346 
Acoin,  164 
Acryhc  acid,  216 

acid  series,  216 


Acrylic  aldehyd,  216 
Activators,  255 
Addition  products,  186 
Adenin,  236 

Adjacent  hydrocarbons,  241 
Adnephrin,  165 
Adrenahn,  165 

chlorid  165 
Adrenol,  165 
Alabaster,  62 
Albumin,  278 
Albumin  in  saliva,  308 

in  saliva,  method  of  determination, 
Dr.  H.  C.  Ferris,  324 

in  urine,  detection  of,  358 

in  urine,  Esbach's  test,  360 

in  urine,  heat  test,  359 

in  urine,  nitric  acid  test,  359 
Albuminoids,  274,  282 
Albuminoscope,  359 
Albumins,  defined,  273 
Albumose,  291,  2gj 
Alcohol,  197 

amyl,  198 

ethyl,  197 

methyl,  197 
Alcoholates,  195 
Alcohols,  195 

atomicity  of,  196 

classification  of,  196,  197 
Aldehyd,  198 

acetic,  198 

acrylic,  216 

benzoic,  247 

formic,  170,  198 
Algaroth,  powder  of,  32 
Aliphatic  hydrocarbons,  186 
Alkah  albumin,  278 

albuminate,  278,  2gi 

metaprotein,  291 
Alkali  protein,  276 
Alkalimetry,  142 
Alkahne  earths,  59 

metals,  69 
AlkaUnity  of  saliva,  304 
Alkahne  phosphates  (in  urine),  354 


387 


388 


INDEX 


Alkyl  (term  defined),  195 
Alkylated  ureas,  234 
Aloxan,  236 
Alloys,  analysis  of,  157 

blank  form  for  preparation  of,  13S 

defined,  108 

dental,  composition  of,  117 

of  bismuth,  25 

of  cadmium,  26 

of  copper,  21 

of  lead,  18 

of  mercury,  16 

of  silver,  14 
Alloys,  preparation  of,  109 
AUylene,  190 
Alum,  45 
Aluminates,  45 
Aluminium,  45 

alloy  for  bridgework,  45 

bronze,  108 

solder,  128 

sulphate,  45 
Alypin,  165 
Alypin  nitrate,  165 
Amalgam  alloy,  108 
Amalgamation  process  (silver  ore),  14 
Amalgam,  defined,  108 
Amalgams,  method  of  making,  112 

tests  for,  118 
Ames's  oxyphosphate  of  copper,  123 
Amido  acids,  221 
Amids,  226 

Amino-acetic  acid,  221,  222 
Amino-acids,  221 
Amino-acids  in  saliva,  320 
Amino-benzene,  246 
Amino-ethyl-sulphonic  acid,  223 
Amino-formic  acid,  222 
Amino-glutaric  acid,  223 
Amino-isobutyl-acetic  acid,  222 
Amino-succinic  acid,  223 
Amino-valeric  acid,  222 
Amins,  226 
Ammonia,  78 
alum,  45 

determination  in  urine,  352 
dilute,  377 
process  (Na2C03),  73 
Ammoniacal  silver  nitrate  solution,  351 
Ammoniated  mercury,  23 
Ammonia  test,  FoHn's,  320 
Ammonium,  75 
acetate,  77 
amalgam,  114 
bifiuorid,  165 


Ammonium  carbamate,  222 

carbonate,  76,  222 

chlorid,  76 

chlorid  in  sahva,  309 

hydroxid,  76 
Ammonium    magnesium    phosphate 
(microchemical  formation),  162 
Ammonium  molybdate,  377 
Ammonium  nitrate,  77 
Ammonium  phosphate,  77 
Ammonium  phosphomolybdate,  162 
Ammonium  picrate  (Exp.  118),  252 
Ammonium  platinic  chlorid,  37 

microchemical  formation  of ,  162 
Ammonium  salts  in  sahva,  309 
Ammonium  salts  in  saliva,  determina- 
tion, 319 
Ammonium  sodium  phosphate,  78 
Ammonium  sulphate,  77 
Ammonium  sulphid,  77 
Amoss,  Dr.  H.  L.,  phenolphthahn,  Ref., 

311 
Amphoteric  reaction  of  milk,  287 
Amyl  acetate,  208 
Amyl  alcohol,  198 
Amyl  butyrate,  208 
Amyl  nitrite,  208 
Amyl  valeriate,  215 
Amylolytic  enzymes  in  saliva,  322 
Amylopsin,  337 
Anaestheaine,  166 
Analytical  groups,  13 
Analytical  reactions  of  arsenic,  27 
Analysis  by  precipitation,  148 

in  dry  way,  96 

of  groups  {see-  Groups) 

of  groups  in  outline,  82  to  84  inc. 

of  sahva,  314 
Anesthol,  166 
Anihne,  246 

oil,  246 

preparation  of  (Exp.  in),  251 
Annealing  of  alloys,  no 
Anneahng  of  gold  and  platinvmi,  in 
Anti-albumin,  279 
Anti-alb uminate,  279 
Anti-albumose,  279 
Antifebrin,  isocyanid  test  for,  229 
Antimony,  alloys,  31 

butter  of,  32 

in  dental  alloys,  116 

metal,  31 

oxychlorid,  32 

potassium  tartrate,  221 


INDEX 


389 


Antimony  stains,  test  for,  33 
Antimonyl  salts,  31 
Antiseptic  tablets,  23 
Apatite,  62 
Apple  essence,  215 
Arabinose,  258 
Argols,  71 
Argyrol,  166 
Arington's  alloy,  117 
Aristol,  166 
Arsenical  pyrites,  26 
Arsenic,  antidote  for,  27 
Arsenic  compounds,  26 
Arsenic  hydrid,  27 

Arsenic,  in  urine,  determination  of,  366 
reactions  for,  27 
special  tests,  28  to  31  inc. 
stains,  tests  for,  33 
volumetric  determination,  148 

Araenious  acid,  26 

Artificial  enamel,  123 

Asbestos,  63 

Asparaginic  acid,  223 

Asparagus,  succinic  acid  in,  218 

Aspartic  acid,  223 

Ash  in  saliva,  325,  326 

Atomicity  of  alcohols,  196 

Atoms,  defined,  i 

Atropine  and  test,  166 

Aciua  regia,  38 

Aurum,  34 

Available  oxygen  in  H2O2  ,  146 

Avogadro's  law,  9 

B. 

Babbitt's  metal,  126 

potash,  72 
Base,  defined,  3 

metal,  12 
Basic  acetate  of  lead,  18 

salts,  3 
Bastard  metals,  12 
Banca  tin,  33 
Barfoed's  reagent, 

test  (Exp.  139), 
Barium,  60 

hydroxid,  60 

peroxid,  60,  171 

salts,  flame  test, 

sulphate,  60 
Barj^ta  water,  60 
Basicity  of  acids,  212 
Bayberry  wax,  215,  268 
Bell-metal,  108 
Benzaldehyd,  247 


377 
262 


61 


Benzene,  240 
Benzine,  187 
Benzoated  lard,  247 
Benzoates,  247 
Benzoic  acid,  247 
Benzol,  240 
Benzosulphinid,  175 
Benzoyl-glycocoll,  248 
Beryllium,  59 

test  for  in  cement,  124 
Berzehus'  test  for  arsenic,  29 
Bile,  338 

experiments  with,  340 
in  urine,  365 

pigments,  Gmelin's  test,  341 
salts,  preparation  of  (Exp.  239),  341 
Binary  amalgams,  113 
Biogen,  171 
Bismuth  alloys,  25 

analytical  reactions,  25 
compounds,  25 
in  dental  alloys,  116 
metal,  24 
ochre,  25 
Biuret,  233 

formation  of,  (Exp.  100),  238 
reaction,  277 
Black  &  Sanger,  Gutzeit's  test,  31 
Black  ash,  73 
Black  wash,  17 
Blaud's  pills,  44 
Block  tin,  33 
Blood,  294 

corpuscles,  295 
corpuscles,  number  of,  296 
in  mine,  371 
plasma,  294 

spvecific  gravity  (Exp.  204),  299 
spiectroscopical  examination  of,  298 
Blue  stone  and  blue  vitriol,  22 
Blow  pipe  tests,  10 1  to  103  inc. 
Boas'  reagent,  335 
test  for  HCl,  335 
Bond,  defined,  2 
Bone,  283 
Bone-earth,  283 
Borates,  93 
Borax,  167 
Borax-bead,  method  of  making,  51 

test,  103 
Brass,  108 

solder  for,  129 
Britannia-metal,  108 
Bromoform,  192 
Bromids,  89 


390 


INDEX 


Bromid,  separation  from  iodids,  91 

Bronze.  108 

Buckley,  Dr.  J.  P.,  Europhen,  Ref.,  169 

Buckley's  phenol  compound,  174 

Butane,  185,  189 

Butter  fat,  208 

Butter  of  antimony,  32 

Butylene,  189 

Butylene-diamin,  226 

Butyric  acid,  213,  214 

Butyrin,  208 

Bynin,  282 


Cadaverin,  226 
Cadmium,  alloys  of,  26 

amalgam,  115 

analytical  reactions,  26 

in  dental  alloys,  116 

metal,  25 

oxalate  (microchemical) ,  162 
Caffein,  235 
Calamine,  53 
Calcium,  61 

in  teeth  and  tartar,  180 

lactate,  220 

oxalate  (microchemical),  162 

oxalate  in  urine,  370 

sarcolactate,  220 

volumetric  determination  of,  152 
Calc-spar,  61 
Calomel,  16,  17 
Cane  sugar.  261 
Carat,  defined,  34 

rules  for  changing,  35 
Carbamic  acid,  222 
Carbamid  (Urea),  232 
Carbinol,  197 

Carbocyclic  compounds,  249 
Carbohydrates,  182 

classification,  258 
Carbolic  acid,  167,  1/4,  242 
Carbonates,  87 

titration  of,  144 
Carbon  dioxide  in  saliva,  304 
Carbonic  acid,  217 

in  teeth  and  tartar,  180 
Carbon,  test  for,  182 

tetrachlorids,  192 
Carboxyl,  212 
Carnallite,  69 
Carnin,  297 
"C.  A.  S."  alloy,  117 
Casein,  288 
Caseinogen,  288 


Cassiterite,  33 
Cast  iron,  43 
Casts,  renal,  371 
Catalase,  defined,  255 
Cellulose,  265 
Cement,  dental,  120 

composition  of,  178 

general  tests  for,  121 
Centigrade  scale,  8 
Centinormal  solution,  139 
Cerussite,  17 
Chalk,  61 
Chases'  copper  amalgam  alloy,  117 

incisor  alloy,  117 
Chemical  afiinity,  2 
Chemism,  2 
Chih  saltpeter,  74 
Chloral,  199 

test  for,  211 

alcoholate,  167 

hydrate,  167,  199 
Chlorates,  94 
Chlorethyl,  192 
Chloretone,  167 

microchemical  test,  163 
Chlorids,  88,  90 

determination  of  in  saliva,  321 

in  urine,  353 
Chlorin,  in  saliva,  titration,  151 

in  teeth  and  tartar,  180 

titration,  152 

in  urine  titration,  354 
Chloro-chromic  anhydrid  test,  90 
Chloroform,  168,  191 

preparation  of  (Exp.  56),  193 

test  for,  211 
Cholesterin,  371 

in  saliva,  312 
Chromates,  93 
Chrome  alum,  46 

iron  ore,  46 
Chrome  yellow,  18 
Chromic  acid,  90 
Chromic  anhydrid,  46 

oxid,  46 

salts,  47 
Chromite,  46 
Chromium,  46 
Chromous  salts,  note,  46 
Chylous  urine,  345 
Cinnabar,  16 
Citric  acid,  219 
Classification  of  metals,  12 
Closed  chain  hydrocarbons,  240 

tube  test,  99 


INDEX 


391 


Cloudy  urine,  causes  of,  345 
Coagulated  proteins,  276 
Cobalt,  analytical  reactions,  51 
Cobaltite,  51 
Cobalt  metal,  51 

separation  from  nickel,  56 
Cocain,  168,  207 
Cocain  and  KMn04,  162 
Cocain  and  substitutes,  differentiation 
of,  177 

test  for,  168 
Coefficients  of  expansion,  106 
Coefficient  of  Haeser,  348 
CO,  Haemoglobin,  295 
Coin  silver,  14,  108 
Collagen,  282,  283 
Colloids,  5 

Coloring  matter  in  urine,  356 
Color  reactions  for  proteins,  277 
Colors  of  salts,  97 
Color  test  for  amalgam,  118 
Colostrum,  289  ■ 
Common  solder,  127 
Completed  reactions,  4 
Compound  ethers,  204,  207 
Compounds,  defined,  i 
Conductivity  of  metals,  105 
Condys'  fluid,  53 
Congo  red,  test  for  HCl,  335 
Conjugated  proteins,  285 
Contraction  test  for  amalgams,  118 
Cook,  Dr.  G.  W.,  on  mucin  in  saliva, 

Ref.,  308 
Cook,  Dr.  R.  H.,  on  determination  of 

uric  acid,  351 
Cooking  soda,  70 
Copper,  21 

acetate,  22 

aceto  arsenite,  22 

alloys,  21 

amalgam,  114 

analytical  reactions,  22 

arsenate,  22 

compounds,  21 

gravimetric  determination  of,  156 

in  dental  alloy,  116 

oxyphosphate  (Ames'),  123 

pyrites,  21 

sulphate,  22 

volumetric  determination  of,  151 
Copperas,  44 

Corrosive  sublimate,  23,  172 
Corrugated  gold,  iii 
Cotton  seed  oil,  217 
Cream  of  tartar,  17,  221 


Creatin  (Exp.  212),  301 

Creatinin  (Exp.  213),  301 

Creolin,  246 

Creosote,  168 

Cresol,  168,  246 

Crushing  strength  of  amalgams,  119 

Cryohte,  72 

process  (Na2C03  ),  73 
Cryoscopy,  9 
Crystalloids,  5 
Crystals,  formation  of,  160 

from  saliva,  326 
Cuprammonium  compounds,  22 
Cupric  oxid,  22 
Cuprous  oxid,  21 
Cyanic  acid,  233 
Cyanic  acid  (iso.),  229 
Cyanids,  88 
Cyanogen,  228 
Cyanuric  acid,  233,  236 
Cyclic  compounds,  249 
Cylinder  oil,  187 
Cystin,  223 

in  urine,  370 

preparation  of,  377 
Cysto-globulin,  275 

D. 

Decinormal  factor,  139 

solutions  defined,  139 

solutions  (various),  142  to  153 
Defibrinated  blood,  295 
Degree  of  acidity  explained,  287 
Dental  alloys,  108 

composition  of,  117 

cement,  120 

gold,  108 
Dentine,  composition  of,  178 
Derived  albumins,  278 
Derived  proteins,  275,  2gi 
Deutero-albumose,  293 
Dextrin,  264 
Dextrose,  259 
Diabetic  sugar,  259 
Diacetic  acid  in  urine,  365 
Diacylon  plaster,  18 
Dialysis,  6 

of  sahva,  327 
Diamins,  226 
Diastase,  261 
Dibasic  acids,  217 
Dichlor  methane,  191 
Dilute  ammonia,  377 

hydrochloric  acid,  380 

lunar  caustic,  15 


392 


INDEX 


Dilute  nitric  acid,  382 

sulphuric  acid,  383 
Dimethylamin,  226 
Dimethyl-amin-azo-benzene     test     for 

HCl,  334 
Dimethyl  benzene,  241 

ketone,  202 

oxalate,  224 
Dioses,  260 
Dioxypurin,  236 
Disaccharids,  260 
Diureids,  defined,  234 
Dolomite,  63 
Donovans'  solution,  27 
Doremus-Hinds  urea  apparatus,  350 
Double  bonded  hydrocarbons,  189 
Dualistic  formulae,  2 
DuctiUty  of  metals,  105 
Dyad-mercury,  analytical   reaction,    24 

compounds  of,  23 
Dynamometer,  Black's,  113 
Dysalbumose,  293 

E. 
Earthy  phosphates  in  urine,  355 
Edestin,  281 
Egg  albumin,  278 
Ektogan,  169 
Elastin,  282,  283 
Electro-properties,  106 
Elements  defined,  i 
Eleopten,  267 
Empirical  formulae,  2 
Emulsification  (Exp.  153),  269 
Enamel,  artificial,  123 

composition  of,  178 
Endelman  on  phenolphthalein,  Ref,  174 
End  point  defined,  138 
Enterokinase,  337 
Enzymes,  253 

properties  and  classification,  254 
EpitheUum  in  urine,  370 
Epsom  salt,  63 

Equations,  method  of  balancing,  4 
Erepase,  338 
Erepsin,  338 
Erythrodextrin,  264 
Esbach's  reagent,  260 
Essence  of  checkerberry,  247 
Esters,  204,  2oy 
Ethane,  188 

Ether,  preparation  of,  205 
Ethers,  204 
Ethyl  acetate,  207 


Ethyl  alcohol,  197 
Ethyl  benzene,  241 
Ethyl  bromid,  192 
Ethyl  butyrate,  207 
Ethyl  chlorid,  169,  ig2 
Ethylene,  189,  206 

chlorid,  189 

diamine,  226 
Ethyl  ether,  205 
Ethyl  hydrazine,  227 
Ethylidene  lactic  acid,  220 
Ethyl  mercaptan,  245 
Ethyl  nitrite,  208 
Ethyl  oxid,  205 
Ethyl  urea,  234 
Eucain,  169 
Eucain  lactate,  169 
Eudrenin,  169 
Eugenol,  169 
Europhen,  169 
Euzone,  171 

Evaporation,  microchemical,  161 
Expansion  of  metals,  106 
Expansion  test  for  amalgam,  118 
Extraction  of  metals  from  ore,  11 

F. 
Fahrenheit  thermometer,  8 
Fat  in  milk,  289 
Fat  in  urine,  372 
Fats,  208,  267 
Fatty  acids,  212 
Fatty  casts,  372 
Fehling's  test  (Exp.  136),  262 

solution,  379 
Fellowship  alloy,  117 
Fen  wick.  Dr.  S.,  on  KCNS  in  saHva 

Ref.,  310 
Fermentation  test  (sugar),  (Exp.  140), 

262 
Ferments,  253 
Ferric  alum,  46 

chlorid,  43 
Ferricyanids,  91 
Ferric  ferrocyanid,  45 
Ferric  sulphate,  43 
Ferric  sulphocyanate,  45 
Ferric  thiocyanate,  45 
Ferris,  Dr.  H.   C,  methods  of  saliva 

analysis,  Ref.,  314 
Ferris's  ureometer,  320 
Ferrous  carbonate,  44 
Ferrous  sulphate,  44 
Fibrin,  295 
Fibrin  ferment,  294 


INDEX 


393 


Fibrinogen,  294,  300 
Fibrinous  casts,  371 
Filtration,  6 

microchemical,  161 
Fine  solder,  127 
Fire  damp,  188 
Flagg's  submarine  alloy,  117 
Flame  test,  100 
Fleitman's  test,  29 
Fletcher's  gold  alloy,  117 
Flow  of  amalgam,  102 
FoHn's  ammonia  test,  320 

method  for  ammonia  in  urine,  352 
Formaldehyd,  198 

method  for  ammonia  in  urine,  352 
Formaldehydurea,  368 
Formalin,  170 

test  for  (Exp.  62),  201 
Formamid,  226 
Formanilid,  227 
Formic  acid,  212,  213 
Formic  ether,  205 
Formine,  170 
Formol,  170 
Formose,  198 
Formula,  defined,  2 
Fowler's  solution,  27 
Fractional  distillation,  187 
French  chalk,  63 
Freund  &  Topfer,  test  for  acidity  of 

urine,  347 
Frohde's  reagent,  173 
Fruit  sugar,  260 
FuLminic  acid,  229 
Furfuraldehyd,  259 
Fusel  oil,  198 
Fusible  metals,  126 

G. 

Gad's  experiment  (Exp.  153),  269 

Galactose,  260 

Galena,  17 

GaUotannic  acid,  176 

Gasolene,  187 

Gastric  contents,  titration  for  acidity, 

(Exp.  229),  336 
Gastric  digestion,  331 

lipase,  332 
Gay-Lussac,  law  of,  8 
Gelatine,  283 

preparation  of  (Exp.  175),  284 
General  protein  reactions,  276,  277 
German  silver,  108 
Glauber's  salt,  74 
Gliadin,  282 


Globin  274 

GlobuUns,  273,  279,  281 
Glonoin,  spirit  of,  173 
Glycerine,  see  Glycerol 
Glycerol,  170,  209 
Glyceryl,  208 

butyrate,  208 

oleate,  209 

pahnitate,  209 

stearate,  209 
Glycin,  222 
Glycocoll,  222 

relation' to  urea,  338 
Glycocollic  acid  in  bile,  338 
Glycogen,  264 

in  muscle,  297 

in  sahva,  321 

isolation  of,  379 
Glycol,  217 

Glycolhc  acid,  217,  2ig 
Glyco-proteins,  285 

defined,  275 
Glucinum,  59 
Gluconic  acid,  259 
Glucosazone,  260 
Glucose,  259 
Glue,  283 

Glutamic  acid,  223 
Glutehns,  282 

defined,  274 
Glutenin,  282 

GmeHn's  test  for  bile  (Exp.  240),  341 
Gold,  34 
Gold,  aluminium  solder,  129 

amalgam,  115 
■  armeahng  of,  in 

gravimetric  determination  of,  157 

in  dental  alloys,  116 

salts,  36 

scrap,  recovery  of,  133 

solders,  129,  130,  131 

volumetric    determination    of,     148, 
154 
Goulard's  extract,  18 
Grain  alcohol,  197 
Gram's  solution,  170,  380 
Grape  sugar,  259 
Graphic  formulae,  2 
Gravimetric  determination,  153  to  158 

inc. 
Gravity,  specific,  9 
Green  vitriol,  44 
Group  I,  analysis  of,  19 
Group  II,  analysis  of,  37 
Group  III,  analysis  of,  47 


394 


INDEX 


Group  IV,  analysis  of,  55 

Group  V,  analysis  of,  64 

Group  reagents,  12 

Groups  I-VI,  metals  of,  13 

Groups  III,  IV  and  V-  analysis,  phos- 
phates present,  80 

Guaiacol,  243 

Guaiacum  test  for  blood  (Exp.  205), 
299 

Guanin,  236 

Gun  cotton,  265 

Gun  metal,  109 

Gunzburg's  reagent  and  test,  334 

Gunzburg's  reagent,  380 

Guttapercha,  170 

Gutzeit's  test,  28 

Gutzeit's  test  (Sanger  &  Black),  31 

G3T)sum,  62 

H. 

Haemin,  296 

crystals,  preparation  of  (Exp.   206), 

299 
Haematin,  295 
Haemochromogen,  295 
Haemoglobin,  295 

crystals,  preparation  of  (Exp.  202), 

298 
Haemoglobins  defined,  275 
Halogens,  test  for,  184 
Haloid  derivatives  of  the  parafiins,  191 
Hard  solder,  127 
Harris's  amalgam  alloy,  117 
Head,  Dr.  Joseph,  bifluorid  of  ammonia, 

Ref.,  i6s 
Heavy  spar,  60 
Hehum,  60 

Hematoporphyrin,  345 
Hemialbumose,  279,  293 
Hemipeptone,  279 
Hemostatin,  165 
Heroin,  170 
Hetero-albumose,  293 
Heterocyclic  compounds,  249 
Heteroxanthin,  236 
Hexoses,  259 
High  grade  alloy,  117 
Hippuric  acid,  222,  248 
Histones,  defined,  274 
Homocychc  compounds,  240 
Homologues,  185 
Hopogan,  171 
Hordein,  282 
Horismascope,  359 
Horn  silver,  14 


Howe,   Dr.   J.  Morgan,  on  KCNS  in 

saUva,  Ref.,  310 
Howe,  Dr.  Percy  R.,  calcium  determi- 
nation, Ref.,  152 
Howe,   Dr.   Percy  R.,   phosphates   in 

sahva,  77 
Hydrargyrum,  16 
Hydrazines,  227 
Hydrocarbons,  184 
Hydrochinon,  243 
Hydrochloric  acid  in   stomach,  333 

test  for  free,  334 
Hydrocyanic  acid,  228 
Hydrogen  dioxid,  see  Hydrogen  peroxid 

peroxid,  171 

peroxide  factor  for,  146 

peroxid  strength  of,    146 

test  for,  182 
Hydrolysis,  254 
Hydrolytic  enzymes,  254 
Hydroquinol,  243 
Hydroxy  acids,  219 
Hydroxy  acetic  acid,  219 
Hydroxy  benzene,  see  Phenol,  174 
Hydroxy  propionic  acid,  219 
Hydroxy  succinic  acid,  219 
Hydroxy  toluene,  246 
Hypobromite  solution  for  urea,  380 
Hypochlorites,  90 
Hypophosphites  (HH2PO2),  91 
Hypoxanthin,  236 


Ignition  tests,  98 
Indican,  see  Indoxyl 
Indicators,  140 
Indol,  250 
Indoxyl,  250 

in  urine,  357 

oxidation  of,  250 

-potassium  sulphate,  250 
Inorganic  matter  in  teeth  and  tartar, 

179 
Inosite,  297 
Invertase,  380 

lodids  and  bromids,   separation  of,  91 
lodin,  decinormal  solution  of,  147 

test  for  bile  pigment  (Exp.  240),  341 
Iodoform,  192 

preparation  of  (Exp.  57),  94 
Ions,  3 
Iron,  43 

by  hydrogen,  43 

compounds  of,  43 

reactions  of,  44 


INDEX 


395 


Iron,  reduction  from  ore,  43 

scale,  salts  of,  221 
Isobenzonitril,  229 

test  for  chloral,  211 
Isobutylcarbinol,  198 
Isocyanic  acid,  229 
Isocyclic  compounds,  249 
Isomers^  185 
Isonitrils,  229 

K 

Kalium,  69 

Kekule's  benzene  ring,  240 

Kephir  grains,  289 

Keratin,  282 

Kerosene,  187 

Ketones,  202 

Ketose,  258 

Kieserite,  63 

King's  occidental  alloy,  117 

Kingzett's  method  for  H2O2  titration, 

147 
Kirk,  Dr.  E.  C,  CO2  in  blood,  Ref.,  312 
Kjeldahl  process  of  oxidation,  183 
Kumiss,  289 


Lacmoid,  140,  243 
Lactalbumin,  288 
Lactates  in  urine,  370 
Lactic  acid,  220 

in  muscle,  297 

in  tartar,  179 

tests  for,  335 
Lactose,  261 
Lactosazone,  261 
Laevulose.  260 
Law  of  Avogadro,  9 
Law  of  Charles,  8 
Law  of  Gay-Lussac,  8 
Law  of  precipitation,  10 
Lead, 17 
Lead  acetate,  18 
Lead  alloys,  18 
Lead  arsenate,  18 
Lead  chromate,  18 
Lead  nitrate,  18 

oxids,  18 

reactions  of,  19 

reduction  from  PbS,  17 

subacetate,  18 
Lead  in  urine,  determination  of,  366 
LeBlanc  process  (Na2C03),  72 
Lecithin  in  saliva,  312 
Lecitho-proteins  defined,  275 


Legal's  test  for  acetone,  364 
Leptothrix,  330 
Leucin,  222,  223 

in  saliva,  312 

preparation  of  (Exp.  231),  339;  also 

377 
Leucocytes,  296 
Limestone,  61 
Lipase,  from  castor  bean,  381 

from  pancreas,  381 
Litharge,  18 
Lithium,  75 

salts  and  uric  acid,  237 
Litmus,  140 
Liver  of  sulphur,  71 
Local  anaesthetics,  164 
Low's  gold  solder,  131 
Lugol's  caustic  iodin,  171 

solution,  171 
Lunar  caustic,  15 
Lymphocytes,  296 

M 

Magnesite,  63 
Magnesium,  63 

carbonate,  63 

in  teeth  and  tartar,  180 

oxid,  64 

peroxid,  171 

phosphates,  64 

sulphate,  63 
Mahe,  Dr.  G.,  on  NaCl,  Ref.,  175 
Malachite  blue  and  green,  21 
Malic  acid,  218,  219 
Malleability  of  metals,  105 
Malonic  acid,  218 
Maltodextrin,  264 
Maltose,  261 
Manganates,  53 
Manganese,  52 

hydroxid,  53 

reactions,  53 

separation  from  zinc,  56 
Mannite,  196 
Marble,  61 

Marme's  reagent,  173 
Marsh-Berzelius  test  for  arsenic,  29 
Marsh  gas,  188 

Marsh's  test  for  arsenic  or  antimony,  32 
Mayer,  A.,  on  KCNS  in  saliva,  Ref.,  310 
McElhinney,  Mark  G.,  platinum  solder, 

Ref.,  131 
Measures,  7 
Meconic  acid,  216 
Meerschaum,  63 


396 


INDEX 


Mellott's  metal,  126 
Melting  point  of  metals,  105 

method  of  taking,  127 
Menthol,  172 
Mercaptan,  245 
Mercuric  chlorid,  23,  172 

oxid,  23 

iodid,  23 
Mercurous  chlorid,  16 

iodid,  17 

nitrate,  17 
Mercury,  16 

alloys,  16 

compounds  of,  16 

excess  of,  in  amalgams,  117 

in  saliva,  test  for,  330 

reactions  of,  17 

recovery  of,  134 

tests  for  purity,  134 
Mesitylene,  242 
Meta-compounds  defined,  241 
Metacresol,  246 
Metalloids,  12 
Metals,  classification,  12 

extraction  of,  11 

occurrence  of,  11 

properties  of,  105 
Metaphosphate  of  zinc,  120 
Meta-protein,  291 

defined,  275 

preparation  of,  292 
Metastannic  acid,  2,?) 
Methane,  188 
Methethyl,  172 
Methyl-alcohol,  195,  197 

test  for,  (Exp.  61),  200 
Methylamin,  226 
Methyl-benzene,  241 
Methyl-bromid,  192 
Methyl-carbamine,  229 
Methyl-carbinol,  197 
Methyl-chlorid,  172,  191 
Methyl-chloroform,  192 
Methylene  chlorid,  191 
Methylene  ether,  205 
Methyl  ether,  205 

ethyl  ether,  205 

hydrazine,  227 

iodid,  192 

orange,  140 

oxid,  205 

salicylate,  207 

urea,  234 
Metric  equivalents,  7 


Michaels,  Dr.  J.  P.,  albumin  in  saliva, 

Ref.,  308 
Michaels,  Dr.  J.  P.,  methods  of  saliva 

analysis,  Ref.,  315 
Michrochemical  analysis,  159 
Microcosmic  salt,  78 
Microscope,  use  of,  159 
Milk,  286 

alcoholic  fermentation  of,  289 

fat,  289 

modified,  288 

plasma,  286 

reaction  of,  287 

specific  gravity  of,  286 

solids  by  calculation,  287 

wine,  289 
Miller,  Dr.  W.  D.,  mucin  in  saliva,  Ref. 

308 
Millon's  reagent,  382 

test  (protein),  277 
Mineral  oil,  186 
Minium,  18 
Mixed  ether,  204 
Modified  milk,  288 

Mohr's  method  of  determination  of  ar- 
senic, 148 
Moisture  in  teeth  and  tartar,  179 
Molecules,  defined,  i 
Molisch's  test  (carbohydrates,  Exp.  133), 

262 
Monobrommethane,  192 
Monochlormethane,  169 
Monasaccharids,  258 
Monsel's  salt,  43 
Monoses,  259 
Morphine,  172 

Morphine,  michrochemical  test,  162, 163 
Mucic  acid,  308 
Mucin,  285 
Mucin  in  saliva,  307 

in   saUva  method   of   determination, 
Dr.  H.  C.  Ferris,  324 

in  mine,  372 
Mucoids,  275 
Murexid,  note,  236 

test  (uric  acid,  Exp.  104),  239 
Muscle,  296 
Muscle  plasma,  296 
Muscle  serum,  297 
Musculin,  300 
Myogen,  301 
Myogenfibrin,  301 
Myosin,  297,  300 
Myosinogen,  297 


INDEX 


397 


N. 
Naphtha,  187 
Natrium,  72 
Nesder's  reagent,  24 
Neutral  salts,  3 
Nickel,  52 

alloys,  52 

coin,  52 

separation  from  cobalt,  56 
Nirvanin,  173 
Nitrates,  94 
Nitre,  70 
Nitrils,  229 
Nitrites,  91 

in  sahva,  310,  322 
Nitrobenzene,  245 

preparation  of  (Exp.  no),  251 
Nitrogen,  tests  for,  182 
Nitroglycerin,  173 
Noble  metals,  12 
Non-cohesive  gold,  in 
Normal  factor,  defined,  137 
Normal  salt  solution  (physiological), 

73 
Normal  solution,  defined,  137 
Novocain,  173 
Nucleo-albumin  in  bile,  340 
Nucleohistone,  275 
Nucleo-proteins,  defined,  275 

O 

Occurrence  of  metals,  11 
Odontographic  alloy,  117 
Oil  of  betula,  207 

of  bitter  almonds,  247 

of  cloves,  173 

of  mirbane,  245 

of  wintergreen,  207,  247 
Oils,  267 

Olefin  series  of  hydrocarbons,  189 
Oleic  acid,  217 
Organic  acids,  212 
Organic  chemistry,  181 
Organic  matter  in  teeth  and  tartar,  180 
Organized  ferments,  253 
Orpiment,  26 

Ortho-compounds,  defined,  241 
Orthocresol,  246 
Orthoform,  174 
Osazones,  260 
Osmotic  pressure,  6 
Osmosis,  6 
Outline  analysis,  group  I-VI,  82  to  84 

inc. 
Oxalates,  89,  93 


Oxalates  in  urine,  370 
Oxalic  acid,  217,  218 

in  foods,  218 

standard  solution  of,  139 

in  tartar,  179 
Oxaluric  acid,  234 
Oxidation  of  alcohols,  198 
Oxidases,  see  Oxydases 
Oxidation  and  reduction,  analysis  by, 

144 
Oxyacids,  219 
Oxybenzene,  242 
Oxybenzoic  acid,  207 
Oxybutyric  acid,  220 
Oxychlorid  cements,  122 

of  zinc,  122 
Oxydases,  255 

in  saliva,  311 

preparation  of  (Exp.  125),  255 
Oxyhemoglobin,  295 
Oxyphosphate  cement,  123 

of  copper,  123 

of  zinc,  1 20 
Oxypropionic  acid,  220 
Oxysulphate  of  zinc,  123 


Palmatin,  215 

Palmitic  acid,  213,  215 

Pancreatic  juice,  339 

Parabanic,  234,  236 

Para  compounds,  defined,  241 

Para-cresol,  246 

Paraffin,  187 

series,  185 

wax,  186 
Paraform,  198 
Paraformaldehyd,  198 
Paraglobuhn,  281 
Paralactic  acid,  220 
Paraldehyd,  199 
Para-myosinogen,  300 
Paris  green,  22 
Pearl  ash,  70 
Pearson's  solution,  27 
Pentane,  185 
Pentoses,  258 
Pepsin,  331 

Pepsin-hydrochloric  acid,  333 
Pepsinogen,  331 
Peptides,  276,  292 
Peptones,  276,  292 

Permanganate,  standardization  of,  145 
Peroxidases,  255 

in  saliva,  311 


398 


INDEX 


Peroxid  of  caldum,  171 

of  hydrogen,  171 

of  hydrogen,  strength  146 

of  lead,  see  Black  oxid,  18 

of  magnesium,  171 

of  sodium,  72,  171 

of  zinc,  169,  171 

titration  by  Na2S203,  i47 
Petrolatum,  187 
Pewter,  2>3 
Phenol,  174,  242 

compound,  174 

difference  from  cresol,  168 
Phenolphthalein,  140,  248 
PhenolphthaUn,  311 
Phenol,  preparation  of  (Exp.  124),  252 
Phenol-sulphonic  acid,  244 
Phenyl-formamid,  227 
Phenyl-glucosazone,  260 
Phenylhydrazine,  227 

test  (Exp.  141),  263 
Phenyl-isocyanid,  229 
Phenyl-salicylate,  247 
Phenyl-sulphuric  acid,  245 
Phloroglucinol,  243 
Phosphates,  89,  p2,  93 

as  urinary  sediment,  354 

determination  in  saliva,  321 

method  for  determination  in  saliva 
and  urine,  153 
Phospho-proteins,  defined,  275 
Phosphoric  acid,  factor,  355 

in  teeth  and  tartar,  180 

volumetric  determination,  153 
Phosphorus,  test  for,  183 
Phthahc  acid,  248 

anhydrid,  248 
Physiological  chemistry,  253 
Physiological  salt  solution,  73 
Picric  acid,  246 
Pine-apple  essence,  207 
Piotrowski's  test  (protein),  277 
Plaster  compound,  63 
Plaster  of  Paris,  62 
Plate  I,  100 
Plates  II  and  III,  162 
Plate  IV,  163 

V,  222 

VI,  261 

VII,  296 

VIII,  327 

IX,  367 

X,  368 
Platinum,  36 

alloys,  37 


Platinum-aluminum  solder,  129 

amalgam,  115 

annealing  of,  in 

color,  for  enamel,  37 

in  dental  alloy,  117 

solder  for,  131 
Pol3Tners,  186 
Polyoses,  263 
Polysaccharids,  263 
Potash  alum,  45 
Potassio-auric  iodid,  36 

-mercuric  iodid,  24 
Potassiiun,  69 

bicarbonate,  71 

bitartrate,  71,  221 

bromate,  70 

bromid,  70 

carbonate,  70 

chlorate,  70 

cyanid,  70,  228 

ethylate,  195 

hydroxid,  6g,  174 

iodid,  70 

iodo-hydrargyrate,  24 

methylate,  195 

nitrate,  70 

permanganate,  52 

phenolate,  242 

platinic  chlorid,  37,  71 

sulphid,  71 

sulphocyanate,  229 
in  saliva,  309 
standard  solution  of,  150 
Potato  spirit,  198 
Precipitation,  9 

law  of,  10 
Primary  alcohol,  196,  197 
Prinz,  Dr.  H.,  on  Phenol-sulphonic  add, 

ref.,  244 
Pro-enzymes,  defined,  254 
Prolamins,  282 

defined,  274 
Propane,  189 
Propenyl,  208 
Propionic  acid,  212,  214 
Propylene,  189 
Protamins,  defined,  274 
Proteans,  defined,  275 
Protein,  defined,  273 
Proteins,  270 

classification  of,  270,  273 
Proteoses,  276,  291 
Proto-albumose,  293 
Prosecretin,  339 
Proximate  analysis,  182 


INDEX 


399 


Proximate  principles,  182 

Prussian  blue,  45 

Prussic  acid,  228 

Ptomains,  226 

Ptyalin,  action  on  starch  (Exp.  214),  p. 

327 

conditions  affecting  action  of,  328 

in  saliva,  309 
Pseudo-nucleo  albumin,  288 
Purple  of  Cassias,  36 
Purin,  235 
Putrescin,  226 
Pus,  defined,  296 

in  urine,  371 
Pyridin,  249 

Pyrocatecbin  (pyrocatechol) 
Pyrocatechol,  243 
Pyrogallic  acid,  243 
Pyrogallol,  243 
Pyrolusite,  52 
Pyro-tartaric  acid,  219 


Qualitative  analysis,  11 

Quantitative  analysis  of  dental  alloys, 

157 
Quinalin,  249 

R 
Radium,  60 
Reaction  of  saliva,  303 
Reactions,  completed  and  reversible,  4 
Realgar,  26 

Red  blood  corpuscles,  296 
Red  lead,  18 

test  for  manganese,  53 
Red  precipitate,  24 
Rees's  alloy,  33 
Reinsch's  test  for  arsenic,  28 
Renal  casts,  371 
Rennin,  332 
Residue,  recovery  of  gold,  133 

of  mercury,  134 

of  silver,  133 
Resorcinol,  243 
Reversible  reactions,  4 
Rhigoline,  174,  187 
Richards,  Dr.,  aluminium  alloy,  45 
Richmond,  Dr.  C.  M.,  fusible  alloy,  126 

gold  solder,  131 
Rochelle  salts,  74,  221 
Rock  oil,  187 
Rose's  metal,  126 
Rule  for  changing  C.  to  F.  degrees,  8 


S. 
Saccharic  acid,  259 
Saccharin,  175 
Saccharose,  261 
Salammoniac,  76 
Saleratus,  70 
Sahcylates,  247 
SaUcylic,  207,  247 
Saliva,  acidity  of,  304 

action  on  starch  (Exp.  214),  327 

acetone  in,  321 

alkalinity,  331 

ammonium  salts  in,  309 

analysis  of,  314 

carbon  dioxid  in,  304 

color  of,  306 

determination  of  ammonia,  319 
of  ash,  325,  326 
of  chlorides,  321 
of  nitrites,  322 
of  phosphates,  321 
of  potassium  sulphocyanate,  318 
of  sohds,  325,  326 
of  specific  gravity,  317 
of  urea,  320 

enzymes  in,  322,  323 

glycogen  in,  321 

nitrites  in,  310 

odor  of,  306 

physical  properties  of,  303 

ptyalin  in,  309 

quantity  of,  303 

reaction,  303,  317 

specific  gravity,  303 

variation  in  composition,  302 

viscosity  of,  315 
Sahvary  sediment,  330 
Salmine,  274 
Salol,  247 
Sal  soda,  72 
Salt  defined,  3 
Salt  of  sorrel,  218 
Saltpeter,  70 
Salts  of  tartar,  70 
Salt  solution,  decinormal,  149 
Sanger  and  Black  (Gutzeit's  test,  Ref.), 

Saponification  (Exp.  150),  268 
Sarcolactic  acid,  220 
Scale  salts  of  iron,  221 
Secondary  alcohol,  196,  197 
Secondary  protein  derivatives,  276 
Secretin,  339 
Sedimentation,  6 
Sediment  in  saliva,  330 


400 


INDEX 


Seminormal  solution,  139 
Semipermeable  membrane,  6 
Sermn  albumin,  278,  294 
Serum,  blood,  294 

globulin,  294 
Silicon  skeleton,  92 
Silver,  14 

alloys,  14 

amalgam,  115 

decinormal  solution  of,  149 

fire  assay,  157 

gravimetric  determination  of,  155 

hydroxid,  15 

in  dental  alloy,  determination  of,  150 

nitrate,  175 

oxid,  15 

recovery  of,  133 

solder  for,  131 
Silver-tin  alloys,  116 
Silver,  titration  of,  149 

of  by  KCyS,  150 
Silvering  mirror  (alloy  used),  33 
Simple  ethers,  204 
Simple  proteins,  273,  278 
Skatol,  250 

Skatoxyl  potassium  sulphate,  250 
Smaltite,  51 
Smelling  salts,  76 
Smithsonite,  53 
Smoky  urine,  345 
Soap,  209 
Soapstone,  63 
Soft  solder,  127,  128 
Sodium,  72 

amalgams,  113 

bicarbonate,  73 

carbonate,  72 

chlorid,  73,  175 

decinormal  solution,  149 

hydroxid,  72 

nitrate,  74 

oxalate  in  urine,  370 

microchemical  crystals,  162 

perborate,  175 

peroxid,  72,  171,  175 

phosphates,  74 
and  uric  acid,  237 

potassimn  tartrate,  74,  221 
pyroantimonate,  75 
tetraborate,  167 
thiosulphate  n/io  solution,  147 
uranyl  acetate,  75 
urate,  in  urine,  369 

microchemical  crystals,  162 
Solder,  127 


Solder  for  aluminimi,  128 

for  brass,  129 

for  gold,  129 

for  platinum,  131 

for  silver,  131 
Soldering  acid,  128 
Solids  in  saliva,  325,  326 
Solubility  tables,  85,  86 
Soluble  cotton,  265 
Solution  explained,  5 
Solvay  process,  73 
Somnoform,  176 
Specific  gra\ity,  9 

of  amalgams,  119 

of  sahva,  303 
Spence,  Dr.  S.  J.,  expansion  of  plaster, 

ref.,  62 
Spermatozoa,  372 
Spirit  of  Minder erus,  77 
Sputum,  306 
Standard  aUoy,  117 
Standard  dentaUoy,  117 
Standard  solutions,  137 
Stannous  chlorid,  34 
Stannum,  33 
Starch,  263 

hydrolysis  of,  264,  328 

preparation  of  (Exp.  145),  265 
Steapsin,  337 
Stearic  acid,  213,  2i§ 
Stearopten,  267 
Steel,  43 

Sterhng  silver,  14,  109 
Stibium,  31 
Stibnite,  31 

Stokes,  reagent,  note,  298 
Stomach  steapsin,  332 
Stovain,  176 

Straight  chain  hydrocarbons,  186 
Stroma  of  blood  corpuscles,  295 
Strontium,  61 

oxalate,  michrochemical  crystals,  162 

salts  and  flame  test,  61 
Sturine,  274 

Substitution    products    of    the    hydro- 
carbons, 184 
Succinic  acid,  217,  218 
Sucrose,  261 
Sugar,  in  saliva,  312 

in  urine,  361 

of  lead,  18 

quantitative  determination  by  Feh- 

hng's  solution,  362 
quantitative    determination   by   fer- 
mentation, 363 


INDEX 


401 


Sugars,  258 

test  for,  262,  263 
Sulphanilic  acid,  248 
Sulphates,  89,  p2 

in  urine,  356 
Sulphids,  87 
Sulphites,  88 

Sulphocyanates  in  saliva,  309,  310,  318 
Sulphocyanic  acid,  229 
Sulphones,  245 
Sulphonic  acids,  244 
Sulphuric  ether,  205 
Sulphur  iodid  (for  blow  pipe  test),  loi 
Sulphur  test,  183 
Supraredahn,  165 
Sweet  spirits  of  nitre,  208 
Sylvite,  69 
Symbols,  defined,  2 
Symmetrical  hydrocarbons,  241 
Syntonin,  278,  291 

T. 

Talcum,  63 
Tannic  acid,  176 
Tannin,  176 
Tartar,  178 

analysis  of,  179 

composition  of,  179 

emetic,  32,  221 
Tartaric  acid,  221 
Taiu-ine,  223,  245 
Taurocholic  acid  in  bile,  338 
Teeth,  analysis  of,  179 

and  tartar,  178 
Temporary  alloy,  117 
Tertiary  alcohols,  196,  197 
Teichmann's  haemin  crystals,  296 

test  (Exp.  206),  299 
Thein,  235 
Thermometers,  8 
Thioalcohol,  245 
Thiocyanate   in   saliva,   determination, 

318 
Thiocyanic  acid,  229 
Thiosulphates,  88 

Thorner,  on  acidity  of  milk,  Ref.,  287 
Thrombase,  294 
Thrombin,  294 
Thymol,  176,  243 
Thymophen,  176 
Tin,  33 

alloys,  33 

amalgams,  115 

cement,  123 
.  chlorid,  preparation  of,  34 


Tin,  gravimetric  determination  of,  154 
Tinstone,  33 
Titration,  defined,  143 
Tollen's  reagent,  201 

test  for  aldehyd  (Exp.  64),  201 
Toluene,  241 
Toluol,  241 
Tribrommethane,  192 
Tribromphenol,  174 

microchemical  crystals,  162 
Trichloracetic  acid,  176,  214 
Trichloraldehyd,  199 
Trichlormethane,  191,  168 
Tricresol,  246 
Trihydroxybenzene,  243 
Tri-iodomethane,  192 
Trimethylamine,  226 
Trimethyl-benzene,  242 
Trimethyl-xanthin,  235 
Trinitro-cellulose,  265 
Trinitro-phenol,  246 

preparation  of  (Exp.  117),  251 
Triolein,  209 
Trioxymethylene,  198 
Trioxypurin,  234 
Tripalmitin,  209 

Triple  bonded  hydrocarbons,  190 
Tristearin,  209 
Tritenyl,  208 
Tropa-cocaine,  177 
Tropaeolin,  335 
Truedentalloy,  117 
Trypsin,  337 
Trypsinogen,  337 
Twentieth  Century  alloy,  117 
Type  metal,  109 
Tyrosin,  223,  248 

preparation  of,  377  (also  Exp.  231), 

339 

U. 
Uffelmann's  reagent,  335 
Ultimate  analysis,  182 
Unorganized  ferments,  253 
Unsaturated  hydrocarbons,  189 
Unsymmetrical  hydrocarbons,  defined, 

241 
Uranium,  standard  solution,  153 
Urates,  deposit  of,  369 
Urea,  232 

and  H2O  (reaction),  232 
and  NaBrO  (reaction),  233 
Urease,  255 

Urea   determined   by   Doremus   Hinds 
apparatus,  350 
by  Ferris's  apparatus  (saHva),  320 


402 


INDEX 


Urea  determined  by  Sqmbb's  apparatus, 

349 
in  saliva,  312 
qualitative  test  for,  348 
nitrate,  233 
oxalate  (microchemical  crystals),  162, 

233 
Urea  (synthesis  of  Ex.  99),  238 
Ureas,  substituted,  234 
Ureids,  defined,  234 
Uric  acid,  235,  350 

and  lithium  salts,  237 

and  Na2HP04,  237 

determination,  351 
Cook's  method,  351 
Folin's  method,  352 
ifopkin's  method,  352 

in  tartar,  179 

proportion  to  urea,  368 
Urinary  sediments,  367 
Urine,  abnormal  constituents,  358 

acetone  in,  364 

albumin  in,  358 

alkahne  phosphates  in,  355 

ammonia  in,  352 

analyses,  373  to  376  inc. 

analysis,  interpretation  of,  372 

appearance  of,  345 

bile  in,  365 

causes  of  cloudy,  345 

chlorin  in,  353 

coloring  matter  in,  356 

epithelium  in,  370 

indoxyl  in,  357 

normal  sohds  in,  348 

phosphates  in,  355 

physical  properties  of,  344 

reaction  and  specific  gravity  of,  346 

sulphates  in,  356 
Urinometers,  346 
UrobiUn,  356,  357 
Urochrome,  357 
Uroerythrin,  357 
Uro-rosein,  357 


Valence,  2 

Valeric  acid,  213,  214 

VaseUne,  187 

Vegetables,  oxalic  acid  in,  218 

Verdigris,  22 

Vinegar,  213 

determination  of  strength,  144 
test  for  malic  acid  (Exp.  90),  224 

Viscosity  of  saliva,  315 


Vitellin,  275 

Volatile  alkali,  78 

Volumetric  analysis,  137 

determinations   {see  individual    sub- 
stances), 142  to  153  inc. 

Volumetric    methods    for    saUva    and 
urine,  150 

W. 

Washing  soda,  72 

Water,  detection  of,  in  alcohol  (Exp.  58), 

199 
Water  of  ammonia,  76 
Waxy  casts,  371 
Weldon's  process  for  chlorin,  52 
White  arsenic,  26 
White  blood  corpuscles,  296 

lead,  18 

precipitate,  23,  24 

vitriol,  54 
Will  and  Varrentrap's  test  for  nitrogen, 

183 
Wilson,  Dr.  G.  H.,  expansion  of  plaster, 

Ref.,  62 
Witherite,  60 

Wohler's  test  for  nitrogen,  183 
Wood's  metal,  126 
Wood  spirit,  197 
Wrought  iron,  43 


X. 


Xanthin,  235,  236 
Xanthoproteic  test,  277 
Xylene,  241 
Xylol,  241 
Xylose,  258 


Yeast,  253 
Yellow  wash,  23 


Zein,  282 

Zinc,  53 

Zinc  alloys,  54 

amalgams,  115 
Zincates,  55 
Zinc  blende,  53 

carbonate,  54 

ferrocyanide,  55 

gold  solder,  129 

gravimetric  determination  of,  156 

hydrate,  55 

in  dental  alloy,  116 

lactate,  220 


INDEX  403 

Zinc  oxalate,  55  Zinc,  separation  from  manganese,  56 
oxychlorid,  122  sulphate,  54 

oxyphosphate,  120  sulphid,  54 

oxysulphate,  123  volumetric  determination  of,  151 

peroxid,  169  white,  54 

sarcolactate,  220  Zymogens,  254 


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RK290 


Smith 


Sra5 
1912 


T.©r»'hllT*e— nn-lroe     rMn      rtVicnv?  e<4"»»-rr     ■(*j-.t»      A/ 


COLUMBIA  UNIVERSITY  LIBRARIES  (hsl.stx) 

RK  290  Sm5  1912  C.1 

Lecture-notes  on  chemistry  for  dental  st 


2002370131 


